well dude...i know you'r keen to share your views on what you read on forums and online and stuff...but allow me to refute this with real-life experience.
I work in a pretty renowned music store that have a few tube amps that are 10+ years old (go ahead, make an educated guess) and I don't run into these kind of problems. Sometimes these amps dont get played for 3+ years and my boss suddenly wants them to go out for rental, so I gotta play the shit out of them to make sure that they are ok. No biggie, no problems with any equipment in that regard so far.
I've also asked our tech on this and this is his opinion on the matter. Caps dont dry up and leak...more likely than not they blow due to malfunction. Often, tube amps go bad due to wear and tear and long hours of usage, tubes going bad, etc.... He even told me that often when manufacturers manufacture caps, they don't go into the amps in question immediately. Sometimes they can even sit on the shelf for up to a year before they even see any action in the amp....
So the chances of caps drying and leaking are as common as hurricane katrina....coming to Singapore!