ok.......I don't know why your whole paragraph is split into sentences like that, but that's really annoying to read....
Thermal pads SUCK
AS5 is the best stuff you can get, and whatever moron suggested that AS5 isn't meant for long term use is just that......a moron.....
use AS5 for a year if you want and it'll be fine, but yes you need to put a new coat on every time you remove the heatsink. AS5 takes 200 hours of heating up and cooling down to reach it's "optimal" stage of cooling efficiency.
Don't ever mix AS5 and a thermal pad together either.