Tube replacement for a SOB

I have a 1 -12 SOB combo from about 1984. Original owner. I had it in the repair shop once, probably 20 years ago and I believe they replaced the tubes among other repairs that were necessary at the time. I am playing now, more than ever and wondering if I should replace my 20 YO tubes? I know tubes are a very subjective topic. I am playing in stereo with a Fender Twin 65 reissue as my other amp. I'm happy with the sound overall, but since the tone may have deteriorated gradually over time, not sure I know what I might be missing. I appreciate any advice!

buy new tubes....if they don't jive with you, throw the old ones back in. If it ain't broke don't fix it, ya know? when it comes to preamp tubes, FOR THE LOVE OF GOD, MAN, LABEL EACH ONE EXACTLY WHICH SOCKET IT WAS ORIGINALLY IN!!!!!!!!!!!!!!!!!!!!!!!!!!

Thanks for the advice. I was leaning towards buying new tubes anyway. I'm not a very technical person, so can you tell me where I'd find the info on what tubes I need (without taking them out and bringing them to a music store) and should I get Mesa replacement tubes or another brand? Again, I know that's a very subjective question. I just don't trust the rookie at Guitar Center to know what is best and welcome opinions from this group. Thanks!

The small preamp tubes are all 12AX7 and your large power tubes are 6L6GC in an SOB, I think. Get Mesa tubes if you want. A million guys will give you a million different views on what tubes you "should" get. Or go to a tube vender like Doug's tubes, tell him what amp you have and he can recommend a good combo of tubes for you. Good luck and have fun with it!

Thank you very much! That's exactly the info and advice I was looking for!