To be honest I am more surprised when someone is full time 40 hours, 5 days a week on the glass than if they are "part time"
I generally work 8:30 till 2:30 Monday to Thursday.
I don't consider myself part time though, I spend at least an hour a day on other tasks including a couple of hours on a weekend sorting van, reminding customers, scheduling and book keeping etc.
I may be part time technically cleaning windows but I certainly feel like I put more work in than I ever did 9-5 in previous jobs,
used to spend most of the day day dreaming and once 5 rolls down you clock out both physically and mentally.
I don't think whether it's summer or winter matters it's still a slog trying to long hours as you are either cold, wet or red hot.