Central Pennsylvania gives a house four fairly distinct problems across a year.
Spring is pollen. It comes through every open window and it lands on sills, blinds, floors, and every flat surface in the house, and it does it again the next day. Plenty of clients go from monthly to every two weeks from April through June and back again after.
Summer is traffic. Doors open constantly, the yard comes inside on everybody's feet, and in a house with a pool or a garden the floors take the worst of it.
Fall is grit. Leaves break down into a fine dark dust that comes in on shoes, and the mature trees in the older Harrisburg neighborhoods make that worse rather than better.
Winter is heating and salt. Forced air moves dust around the whole house rather than letting it settle, radiators bake it onto surfaces, and road salt comes in on boots and eats at entry floors. It is also when the house is shut up for months, which is why a lot of people book a reset in January or February rather than waiting for spring.
You do not have to change the schedule for any of this. But if a month feels worse than the last one and nothing else changed, the season is usually the reason.