In position 500bb deep, calling dominates: their range is strong but capped by the depth itself.
4-betting narrows to the very top; suited hands with nut potential call more. The question on every street becomes: which hands are happy getting 500bb in?
The big blind 3-bets your middle open. Out-of-position 3-bets skew honest — adjust your continues accordingly, and enjoy position all hand.
Assumes a standard 3-bet; 4-bet to ~2.2–2.5x the 3-bet. Deep, favor calls over 4-bets — a 4-bet pot at 500bb+ commits you with range disadvantage.