I pull my drives yearly and check for alignment, lube etc..

Should the gaskets/o-rings be changed everytime the drive is removed? or can they be reused?

I know some folks don't replace them & have no issues. However, since a kit is only $6 I replacethem every time I pull a drive.

If they are still properly glued in place, not cracked or hardened, I reuse them. Never had a problem. I always apply a film of lithium grease on them before reinstalling the drive.