Regarding the seals.
The answers there will be revealed with time, the quality of antioxidants and plasticisers used will be crucial for long life, something easily cheaped out on, with no immediate indicators.
Obviously as things become NLA or outrageously expensive the temptation to use cheap or alternative items becomes stronger, but (important) rubber items are never something to save money on.
But realistically many of the saws here are low use, so any mechanical parts that appear up to the task when installed will probably live a long happy life (bearings withstanding), but that lovely pliable rubber/polymer part, if it's not borne of quality it's going to degarde and fail if used or not.
Would I use AM seals, in my own saws, yeah, they aren't normally hard to change, and failures will be noticed and non catastrophic, saws that run every day? something else will probably fail first.
I imagine people here would have received the occasion old stock rubber item, only to find it perished?
That said, in my real job, I will not use non branded rubber products of any kind, unlike many machinery parts, rubber items don't have the tell tale signs of quality to go off when considering if they are fit for purpose, it's just too hard to tell.
Bearings? if a standard size, I just get them cheap locally, skf, fag, ntn, nsk, any quality name should do.