As far as your rules go, it would be of greater benefit to everyone if you actually worked with me to figure out why they aren't working. Just reverting back to the old version without giving me a chance to diagnose the problem will just delay the problem until later when you find you have to upgrade again.
Also, sorry if I was a bit snippy about the upgrades but I didn't want anyone to get the false notion that I'm doing paid upgrades that frequently. There are people out there who have complained about me charging for an upgrade, many times based on incorrect data, like what you implied with the 1.5-2 year cycle. Just remember that the product pre-dates your use of it.