I visited Patmos briefly in 1999, staying just two days.
I returned in 2021 for a four-day visit.
This trip was during late September, one of the "shoulder seasons" of mid-April through May and September through mid-October. Businesses are open, the ferries are operating nearly full schedules, and things aren't crowded. The small Patmos harbor isn't filled with an enormous cruise ship disgorging a swarm of passengers. It's much more pleasant than the high season.
Here are the pieces of that visit in order:
Or, Continue Through Greece: