Maintenance for Tube Preamps

Other than periodically replacing the tubes (and they generally last longer than most people think), I would just occasionally treat all of the contacts with Caig Deoxit or Cramolin. You don't need much of it at all, but I think it's a good idea. For a quick treatment, just spray a tiny amount of deoxit into the end of your interconnects and then plug it in and rotate the end to spread the love.

I'd also advise testing your tubes before replacing them. Don't replace based upon some arbitrary limit. If something starts to sound wrong or you blow a fuse, test all the tubes. You can probably find an old Eico dynamic tube tester on eBay for about $200 or less.

The only other thing I could think of is just opening it up and making sure to keep it clean/dust free inside.

Generally speaking, if something is wrong you will most likely be able to hear it. The problem with proactive maintenance (especially with vintage gear) is that you can change the tonal quality - and not necessarily for the better.

Contact cleaning is fine. I would advise against changing/replacing any internal parts other than tubes if the preamp is working fine.

Cleaning connections on a regular basis is a good practice, but I advise against products that leave a film because over time it can get messy and cause problems. A good electrical contact cleaner that leaves no film is your best bet.

Rrog and sibelius offer good avdice. Cramolin, is great at first, then leaves black goo...not good. Clean and connect. Change tubes when noise is an issue. Jallen

Thanks to all who responded - good advice! A bit of contact cleaning is probably a worthwhile thing to do.