Your pressure test sounds good. orrelse is right...even a slow leak is unacceptable and will drain all your gas overnight.
If they're new kegs, definitely take them apart and clean the posts, the down tube, change O-rings and all that.
For general sanitizing, we use Iodophor, then put a little pressure on them to test, push the poppet down on the outflow so it gets purged with sanitizer, then flip it over and push the poppet on the inflow so it gets purged with sanitizer. Every so often, you should take them apart for a thorough cleaning. Being sure to rinse them immediately after they're empty is key to saving effort.
Cheers!
