October to February: the short winter and the jobs that belong in it
Winter is when the pool finally stops fighting you, and the temptation is to stop paying attention. Resist it, because the cool months are the only sensible time for disruptive work. Anything that requires draining or half-draining the pool — acid washing tired plaster, regrouting the tile line, replacing underwater lights, repairing expansion joints — belongs between November and February, when refill water will not immediately cook and the pool being out of action for a few days costs nothing socially.
Winter is also when total dissolved solids should be dealt with. After a full summer of evaporation and dosing, a partial drain and refill resets the water chemistry and makes the coming year's chlorine noticeably more effective. Municipal rules on discharging pool water vary by emirate, so a professional who knows where the water is allowed to go is worth having.