It already makes a difference that the watch3 is almost 4 years old, so it will probably also lose weight with new watchOS (of course does not mean that it is immediately unusable)
I had not recommended the 3 anyway since the 5 was out, then buy the 4 somewhere cheaper than at Apple.
It is indeed good that Apple has been supporting for so long, but maybe with the watch3 they might have had to release a smaller WatchOS7 with less functions or something.
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