When you rent a movie via the iTunes Store, you have 24 hours from the time you start watching the movie until it is erased from your drive. That’s marginally better than the situation with Comcast (my cable provider). With Comcast, the 24 hour clock starts ticking from the moment I rent a movie, whether I start watching it immediately or not—making me feel a bit like Jack Bauer in 24. With the iTunes Store, you have a generous 30 days within which to start watching the movie.

The problem for me, even with iTunes Store rentals, is that I often want to watch a movie over two nights. The 24 hour limit gets in the way here. If I start watching at about the same time each night, I won’t get to see the second half of the movie—because I will have exceeded the time limit. A 36 (or even a 30) hour rental would make so much more sense. I know I am not alone here. A recent column by David Pogue makes the same point.

This is one reason I never rent movies from Comcast. It’s also a reason why I have been reluctant to try rented movies from the iTunes Store. Still, I downloaded one the other day, primarily as research for an article I was writing.

With the movie now on my drive, I naturally began to wonder exactly how strictly the 24 hour limit was enforced.

It turns out that it’s not enforced all that much.

What did I do? The most obvious thing I could think of. I changed the time. More specifically, after starting to watch the movie and putting the 24 hour countdown in motion, I went to the Date & Time System Preferences pane. From here, I unchecked the option to set the time automatically. Then I pushed the clock back a day.

Sure enough, iTunes now said that the movie had an extra day remaining before it expired. I still wasn’t sure that this would have the desired effect. But it did. The 24 hour period passed and the movie continued to play.

With success coming this easy, I figured I couldn’t be the first person to have come up with the idea. I was right. When I did a Google search, I found several similar reports.

There are couple of hiccups that can occur if you start pushing times around. iTunes may get a sense that something is a bit off. Occasionally, especially after changing the display size via iTunes’ View menu, the movie window may go gray or the sound may stop playing. Often, just closing and reopening the movie a couple of times will get things working again. As a last resort, I found that if I quit iTunes and reset the clock to less than 4 hours from the expiration time, the movie would always work fine when I relaunched iTunes.

I’ve made no attempt to see whether the extended time limit would hold if I transferred a movie to an iPod or an iPhone. I see possible complications here, as these devices have their own clocks. But I leave that for someone else to worry about.

In any case, I imagine that Apple will eventually find a way to prevent these time extensions from working. But who knows? Apple at first tried to block iPhone users from creating their own ringtones for free. In a 180 degree turn-around, Apple later not only ended the blockade but offered tools for creating ringtones using GarageBand.

I have only two theories for my snake-bit relationship with FM tuner iPod car kits: Either I am the most unlucky person to ever use one of these devices or there is something fundamentally wrong with the technology.

A brief bit of background is in order here. I am talking about those devices that allow you to play an iPod via a wireless connection to your car’s FM radio. You connect the iPod to the device, tune the device and your radio to the same “empty” frequency and, voila, you hear music. That’s the idea anyway.

I first wrote about my experience with such devices in a User Friendly View column back in 2005. Undeterred by my unpleasant experience with a Griffin iTrip, I gave these devices a second chance with a RoadTrip+ from Newer. At first, it worked very well and I raved about it in the article. Unfortunately, by the end of the next two months, the RoadTrip+ stopped working altogether. Dead as a doornail. I dumped it and returned to my trusty (if clunky) cassette tape adapter.

In 2007, I gave these FM adapters yet another try. This time it was a Belkin TuneBase FM. Similar to the early stages of a romance, I was giddy with joy at first. The device worked as well as or better than any adapter I had ever used (including some I won’t even mention here). Sadly, over time, I was burned yet again. Interference problems kept getting worse and worse. Eventually, no matter what frequency I tried, I kept getting bleeding from other nearby stations or incredible static or both. The TuneBase eventually joined the iTrip and the RoadTrip+ in my ever expanding iPod accessory graveyard. Meanwhile, my old Sony cassette adapter, like the proverbial phoenix, rose from the ashes and was put to work again.

Fast forward to last week. I returned to my adapter roots with another Griffin iTrip. This time it was a new iTrip Auto with SmartScan, a device I had acquired at last month’s Macworld Expo. My initial testing yielded a pleasant surprise: the SmartScan feature worked incredibly well. Instead of me having to locate the best available frequency, the iTrip effectively and quickly did the locating for me. It also appeared that, over the intervening years since my first iTrip, Griffin had managed to considerably improve the audio quality of these devices. I still heard some low-end hiss, but the sound was overall much better than I would have expected.

Flush from the success of this initial encounter, I was ready to give the device a full workout. I would be driving from San Francisco down to Santa Barbara for the week-end. I wanted to listen to an audiobook on my iPod along the way. The new iTrip, which also charges the iPod while it was playing, was just the ticket.

For about the first two hours, all went exactly as planned. I was happily enjoying the book. Then I stopped for gas. Once I was back on the Interstate, I turned on the radio, pressed the iPod’s Play button and heard: nothing. Well, that’s not exactly true. I heard some hiss. Taking a careful look at the iTrip’s screen (which is hard to do in bright sunlight), I determined that there was no readout. The charger light was still working, but the FM transmitter part of the device was dead. I couldn’t believe it. Not again. Not after only two hours.

Have I offended some voodoo practitioner in a former life? Or do all of these devices simply suck? I don’t know for sure. I have to assume that not every new iTrip dies after two hours of use. But I no longer care. I surrender.

As for my drive, there is a happy ending of sorts. Anticipating that the inevitable might happen, I had thrown my cassette adapter in the glove compartment just before leaving. It worked, as well as ever, for the remainder of the trip—just as it had done for the past 5 years.

I know. My next car will not come with a cassette player. I’ll deal with that problem when the time comes.