With the exception of the 48hours after a meal you could handle every day for about 15 minutes. Some people have snakes that can be out for longer but I never bother them for very long. Some snakes deal with handling better than others. You will get to know what your snake can handle after time.

What you need to remember is that handling is a stress factor to your snake. Some are better at dealing with that stress factor than others. At first I would stick to 15 minute handling sessions every other day.

If your snake feeds that week and the next week you want to try handling for 20 minutes then go for it. If at any point he doesn't eat then I would stop handling until he starts to eat again. I would then take a step back and look at what I did differently that week that may have cause him not to eat.