What should I charge for Drop-Ins longer than 30 minutes?

Do you have a daycare charge? if so, that's what I would charge for the 3-4 hour visit. Otherwise, for one hour your rate would be $40. 3 hours = $120. You might offer them your overnight rate of $45 which covers both dogs. That works out to be about $10-12 an hour, which is reasonable. Or you might try offering an hourly rate.

I had a client last year coming in from out of town who wanted to pay an hourly rate of $10 per hour for me to keep their 2 dogs off and on over a 3-day weekend. We calculated out what the entire charge would be. They then booked it as 3 overnights, and I edited the total to reflect what we had agreed on.