Chronomaster: 4 1/2 sec band over 5 years with new movement; what do I do now that batty is dead?

Thanks, guys, for your comments. And Hans, for explaining why my Citizen lost two seconds and not only one. I suppose that this is more likely to happen when the battery has weakened.
I see that the Grand Seiko has a mechanical control for rate adjustment. It's not clear to me whether that changes an internal digital value or an analog trimcap, but in any case it is nicely accessible. The online photo of the A660 movement shows no access to the inside other than by several probe-able electrical contacts. I'm not ready to try to guess how to use those.

Tom, here is an old photo of my Chronomaster on my timing setup. It looks good as new today after being worn for most of 12 years.

Batteries are arriving from Amazon on Tuesday, when I will install one unless something changes my mind before.

Ok, I replaced my Chronomaster battery. The last person to replace the back in Japan torqued it down very hard; I needed to make a simple but sturdy jig to hold the watch case when I removed the back.

Anyway, in the few days on the new battery the watch has been running fast at an average of about 4.1 seconds/year, worn 24 hours per day except while showering or measuring. As is my habit, I include a graph. The variation in slope among the segments may be due to ambient temperature changes.

Thanks for your comments and suggestions!

wbird: hmm, I didn't look into this. I just replaced the battery with a drugstore Duracell 370/371. Oh well, when this cell runs out I'll probably be ready to set the time again anyway.