A halfway decent mechanical watch shouldn't drift more than 10 seconds a day. If it's off by that much, it needs to be fixed/services, but that's not economical

A halfway decent mechanical watch shouldn't drift more than 10 seconds a day. If it's off by that much, it needs to be fixed/services, but that's not economical on most Seikos. If the movement is cheap enough, or if there's a cheap clone movement available, I think you just take the watch apart, separate the hand and face from the old movement, attach the new movement, chuck the old parts in the trash, and put it back together. There are reasons the world moved on, but that doesn't mean you can't appreciate the old tech either.