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I would say that, particularly here, a drysuit is good for all seasons. The insulation needed from the undersuit might change but the suit itself shouldn't. That said, I probably wouldn't use a drysuit in warm water (over 20 deg C).There is no such thing as one suit(wet/dry) for all seasons.
I dive with multi-layers and that depend on water temp.
For me wet suit never last for more than 3yrs as it got compressed and general wear and tear. But a BP/W will last a lot longer as long as the plate and the wing are compatible with your style of diving.
BTW, I bought wet suit first in the beginning and it was the first to disappear from my scuba kit.
Good luck.