How long does AS5 last?

I've had some Arctic Silver 5 for about 4 years now. It's been sitting in my toolbox at room temp the whole time tube closed. Is it still good?

Artic Silver is 99.8% micronized silver, so it should never "spoil." However I would squeeze it and make sure there has been no consistancy change in the tube (a toothpick to poke at it when it's on your CPU would work great).

Hope this helps.