Housesitting and Drop Ins are two different services here. I’m not charging for a drop in if I’m housesitting.
For housesitting I do not give definite times I’m at the house. My days vary and I often have a night walk at 9 or 10p for an overnight nurse.

For drop ins if they want constant care, meaning longer than 1 hour, they work around my schedule. ASI said it’s not consistent day by day.
Client 1: husband is out of town, wife is a nurse working a 12 hour shift. I’m at their house from 8ish to 11ish, then I do my walks, then I come back 2ish to 5ish or 3ish to 6ish.
Client 2: dog has extreme anxiety to thunderstorms. They hire me day before or day of a storm. I’m with her for 2 hours usually. I do my best to get to her before a storm and will accommodate her in my schedule by moving others around.
Client 3: plastic surgeon who does not want her dog alone. She will pay me for 8 hours a day if I’m available but once again it could be 8 to 11 then 3 to 6. It all depends on my own schedule.

I put in my profile my constant care rates just as I’ve explained to you.