What each visit is actually for
Spring is the salt reset
Salt spray off the street and ice melt tracked up the walk leave a dull haze on lower windows and storm doors that lasts until somebody takes it off. The early-spring visit clears that film before pollen sticks to it, which is why bi-annual properties are scheduled for March rather than May.
Summer is the visit that prevents etching
Sprinkler overspray is the single most common thing we treat in this metro, and it does its damage in the months the irrigation runs. A summer visit takes the minerals off before they set into the glass, which is the difference between a clean and a restoration.
Winter is the interior visit
Low winter light shows every streak, which makes it the worst time of year to have dirty interior glass and the best time to have it cleaned. From November through March the windows do not open and the furnace runs continuously, so cooking residue, dust and woodsmoke settle as a film on the inside of the pane.
Fall pairs glass with gutters
Doing both on one trip is materially cheaper than two appointments, because access and setup are most of the work on any small job. It also gets the gutters cleared before the freeze, which is the point at which a blocked run stops being cosmetic.