I use my Speedster a lot, at least weekly, because I enjoyed it so much when first used it for hiking that it now comes with me wherever I'm outdoors to make a brew-up on the go. There's no way this is (or is intended to be) a high-end luxury item, hence my buying a bagful of them so that I can start a new one each year. The threads are going to wear, the interior gauze stuff will eventually break down, the lid's liner will eventually detach and deform. Treat it with respect and it will be fine for a good while.
I only had a 'can't get it off' problem with the threads once, and that was because I'd threaded it badly when doing it up, I think because it was still too warm from use. Still came off after a little coaxing. I wouldn't try to leave fuel inside it other than temporarily.
The important thing is, as I see it, it's not going to suddenly malfunction to the extent that it can't be used. This cannot be said of a gas stove or petrol stove, where if valves, joints, etc fail you may well not be able to effect a repair on the hill.
If you're that worried, you can always take a spare - perfectly viable at 12g a throw!