I used artic silver and never had to reapply, and was going to use it, but was told it's really old school (was over 15 yes ago)...its also electrically conductive so if you make a mess can fry your mobo...hence why I started reading up a bit. The mx4 and mx5(this years stuff) is artic's more modern pastes which are long lasting and non conductive. They require a 24 hrs curing after application though go fully dry etc but then good to go. Just not quite as good as the noctua in my opinion, but to be fair, think unless you doing serious over locking, they'd all be fine