March to May: the pre-summer service window
The eight or so weeks before June are the most valuable in the pool year. The water is warm enough to work comfortably but not yet hot enough to punish mistakes, and every serious technician in the country knows that whatever is marginal in April will fail in July. This is when the annual equipment audit belongs: pump seals and O-rings checked for perishing, the pressure gauge on the filter verified against a known-clean baseline, timer settings reviewed, and the skimmer weirs and baskets inspected for cracks.
Salt-system owners should have the chlorinator cell pulled and descaled before summer, because cell output drops exactly when demand is about to double. If you are comparing providers for an annual contract, this is the sensible moment to do it; the tamam app lets you put the same scope in front of several verified pool companies and compare their AED ranges before the summer rush starts.