They didn't (except in the sense that there is a few months time skip between each season). With season 2 taking place in October-November of '84 (with a Winter Ball sequence in December) and season 3 taking place in the Summer of '85 the space between seasons 2 and 3 where this is set is (I think) the shortest "time skip" between any of the seasons.I didn't realize or maybe remember that they had a time skip.
Yeah, that's probably the sweet spot.I suspect the time frame was chosen not because it was a long interseason time skip but because it's the interseason time skip after Max has arrived and before the Bylers and Eleven move to California (so the whole middle school crew is assembled).