Should I update my GPU drivers?

I would say yes to updating your Gpu drivers because of the Updates for games and may or may not function properly if not updated.

you don't need to change thermal paste every 3 - 6 months, you should always read the manufacture recommendation / use of the product on how long a thermal paste will last. For instance Artic silver lasts around 7 year's or so. I would decompound my PC every 4 - 6 years depending on the heat that my Cpu and Gpu is at.

As for cleaning you should clean your Pc from dust at least Twice a year with no animals in house and around three to four times with animals in the house depending on how much fur, dander, and dust is floating inside your pc. The better you maintain your pc and components from over heating the longer the PC will last.