Generator to power Fridge

Typically I plug the RV into the house the day before leaving to get the Fridge cold. Our trips though have been a day to get to a campground and plug back into power so the fridge just stays cold.

Leaving on a bigger trip soon. Will spend 3 days on the road with overnighters at travel centers before getting to a campground and power.

I understand I can run my generator while driving to run the fridge.

My question is how often should I do that to keep the fridge cold? Guessing (and hoping) I don't run the generator all the time going down the road?

Or maybe If I start out with a cold fridge it's just a matter of running the generator each night to keep it cold for the next day?

thanks