"Powermatic 80" and "Caliber 80" are rebrands of the ETA C07 series movement. There are several subtly-different variations within that series, but they're all essentially an ETA 2824 with the beat rate tuned down to increase the power reserve. The movements are easily serviceable, although general practice in that price range is to just replace the movement at service time; it's cheaper and easier than actually servicing them. Any mechanical watch will easily last a lifetime with regular maintenance, and cheaper watches with common movements will have the best longevity because they're the easiest to service over the long term.
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After reading so much about these movements I feel like that baby alpinist Seiko will be the better choicecause it will be cheaper and easier to maintain with local watchmaker.
Someone more knowledgeable can confirm, but as you pointed out there are numerous Powermatic 80's. The base one has a plastic pallet fork but the higher end ones don't.
That being said, their service costs are pretty low - Tissot charge not too bad compared to a good jewellers given the guarantee etc. They technically don't "repair" movements and just swap it out but that doesn't matter you at the end of the day.
Will it last 20+ years? Eh maybe not. 5-10 years yeah that's fine
People complaining about the plastic part don't know what they're talking about, it's not like it's going to disintegrate in a couple months. It's durable and self lubricating.
The real issue is that it's corner cutting on a luxury item, but that's a different discussion.
I want to service it locally as sending is not that easy