Physical damage: I know of a memory stick that was found in a car park, in a puddle of water, and it had been run over by a car. It was well crushed.

The plug was still in one piece. When it was plugged into a usb port it revealed a whole stack of company details. All perfectly usable.
The moral: Password your documents and take care of your USB memory stick.

I'd guess you were initially concerned about read-write reliability. I would have thought that the chance of physical damage from shock, high or low temperatures, moisture, static, etc., or even loss, would be the most likely issues to be concerned about.

I have never had one fail on me, so far.

They do have a definate lifetime, with varies depending on the specific memory technology used, as well as the internal firmware. Flash memory "wears out" over time - each write reduces it's remaining life. Over the past few years, flash memory life has been extended considerably to the point where it is not a practical concern for most users. However, if you are not a "typical" user, this may be of some concern.

Most flash memory has internal firmware (or, in some cases, host software) that "levels" writes so that each cell or section gets approximately the same number of writes as others. This is a particular problem unique to flash memory which is the reason for some peculiar characteristics of flash memory file systems.

You'd best consult the manufacturer's specifications.

Physical damage: I know of a memory stick that was found in a car park, in a puddle of water, and it had been run over by a car. It was well crushed.
The plug was still in one piece. When it was plugged into a usb port it revealed a whole stack of company details. All perfectly usable.

Wife ran mine through the washer and the dryer. I picked it out of the lint trap (with a few grumbles).

When I plugged it in it was working just fine. I was pretty amazed I must say.

WBF

You'd best consult the manufacturer's specifications.

I'm using Kingston, the spec. is as in my post above.

I'll continue to run the server from the stick, the convenience out ways having to replace it when it fails.

Plus the replacement is likely to have twice the capacity, be twice as fast, and half as expensive!

If I understood your post correctly, you mainly have static software stored on the USB stick. In that case it should last tens of years. The only problem would be if some temporary file or directory on the USB stick is heavily used and rewritten every second or so. In that case you may burn a few hotspots in the USB stick, especially if the sticks firmware doesn't rotate the write blocks as jtara mentioned.

The only USB stick that failed on me was one where the connector was seperated from the stick due to physical damage.

The only USB stick that failed on me was one where the connector was seperated from the stick due to physical damage.

Yes that is the vulnerability. I had a forgotten one stuck in the side of a monitor that I put in my car's back seat. The USB drive bent over slightly and never worked again.

If I understood your post correctly, you mainly have static software stored on the USB stick

Most of the files won't change, for example the apache, php, mysql program files.

Some will change occasionally - as I change web pages etc. Others will change more frequently - mysql databases etc.

I don't see it being a problem, the stick is purely for my own use, to learn php and mysql. I guess I'm unlikely to rewrite the most used files more than a couple of dozen times a day, and as this is a spare time project I won't be doing it every day.