Question about flash drives

It's impossible to answer with any great certainty. It's a bit like asking how long before a car breaks down? Nobody knows for sure.

There are lots of factors, as you've expressed usage is one of those factors, with quality of parts (memory) another key factor.

I would guess in your situation a couple of years, but then I could just as easily guess a couple of months and still be right.

Manufacturers usually specify an expected maximum number of write cycles for a drive, so you could calculate how many you perform on average per day and figure out how many days usage that would give you before you hit the max. Even then, there's no guarantees of course (and you'd somehow have to factor in prior usage). As you can see, this is far from an exact science.

Your best approach would be to consider Flash drives disposable and keep a backup of your Flash drive if at all possible. (e.g. periodically burn the contents of your flash drive to a CD or other media).

I would give it maybe 2 years if it's a decent quality drive.

I'm not 100% sure about this, but I heard that larger drives (>8GB) deteriorate more quickly.

Better to stick with hard drives for portable apps, and there are a few really good reasons why.

First, price per gigabyte. The biggest flash drives are 128GB AFAIK and they'll run you well over $100. Corsair's top-of-the-line Flash Voyager GTR only comes in 128GB and will run you $300. My Seagate Expansion Drive was $49.99 shipped from the Egg. You cannot beat that (get a 128GB flash drive for under $25) with flash. Don't go looking, it just won't happen.

Second, speed. The best flash drives top out around 30MB/s (read or write). This would be considered a damn good flash drive. Cheap flash drives are lucky to get a third of that. Your average Corsair, OCZ, or Patriot (good quality enthusiast flash drives) get around 25. But a cheap external hard drive can do 40-45. Yeah, my $50 hard drive is outperforming the best Corsair flash drive at a sixth the cost and with twice as much storage space.

Third, wear & tear. Flash drives and hard drives are two different animals altogether. A hard drive has metal platters which store data magnetically. Once written, the drive does not require constant power to retain data. Flash drives work more like the RAM in your computer. They store data, but the data is lost when power is lost. Flash drives get around the need for a power source by "flashing" the chip. This can only be done so many times, and when it can't be done anymore, your flash drive starts acting real stupid all of a sudden. And every time the drive is written to, that's a write cycle, that's a new flash. So when you have something like Portable Firefox which is constantly writing to the drive, so while you're just browsing the web, it's murdering the crap out of your drive giving your drive one heck of a workout. Meanwhile, hard drives are meant to run applications. Always have been.

I had a 4GB Corsair Readout, a pretty good drive... it lasted about 18 months. And I don't doubt that some of these guys here have drives that have lasted years and years. Stranger things have happened, but I still have them beat on speed and price per megabyte/gigabyte, so longevity isn't everything.

(It's only fair to point out that a flash drive, particularly a sturdy one like the Corsair Flash Voyager, will take a heck of a lot more abuse than any hard drive. These drives can be boiled, frozen, even run over by a regular car, and they still work. You can't do that with any hard drive. But they're also very easy to lose! Ever lose a cigarette lighter? A flash drive is the exact same size.)