Seiko says they can service my 1996 7S26 "caliber" watch for $125. Guarantee is 12 months. There are a myriad of private watch smiths, each a sole proprietorship with various certificates and experience.

For a treasure like this, which is working well, a preemptive service might extends its life even further.

But, I'd rather not have parts replaced, without them being equally vintage. It's kind of like sending a revolver to Ruger...you just don't know what will happen to it, and they decide.

Any recommended solutions?

Is DIY an option?

After seeing several YouTube videos, DIY is NOT remotely possible. Ultrasonic cleaners, the right cleaning solution, watch case fixture, case back wrench, bezel wrench, tweezers of incredibly small size and sharpness, magnification devices, hand pullers, and of course, a thousand finger cots are all needed. And steady hands. And parts. And courage.

I'm guessing Seiko will replace the entire movement if they find problems.

At the recommendation of Sunset_Va on this forum, I had my 6139 movement overhauled by Klien Vintage Watch Repair in 2016. Mine was a '78 model and Seiko wouldn't service anymore. It required more than your typical cleaning and oiling.

Spencer's email is kleinvintagewatchrepair at gmail dot com

His service is excellent and you should be prepared to compensate him accordingly. He is in very high demand and should be prepared for an extended lead time. However, once he get's to you, you mail him your watch. He get's to it timely and provides a video link of his assessment. He'll provide a detailed estimate before any work is done. I'd say he's extraordinarily transparent.

It's been 9 years and the watch has performed flawlessly since. I'm very happy with his service.