Opening my PS3 Slim for a shell swap, what maintenance should I do while I'm in there?

I'm going to open my PS3 Slim to replace the shell and give it a thorough cleaning. Since I'll already have the console disassembled, I want to make sure I do any worthwhile preventative maintenance now rather than having to open it again later.

I only meant to clean it and replace the shell but what other common things I should do while it's apart? Should I replace the thermal paste or replace the CMOS battery, is that worth it?

Any maintenance mods or upgrades people recommend for long-term reliability?

The console works fine at the moment, so I'm mainly looking for preventative maintenance and longevity tips.

Thanks!