It seems like there is an endless possible number of days on vs days off with PE routines. 3 but I think preferably 4 exercise days per week is fine and the most important thing is to make it fit your schedule, so PE doesn’t become a hassle that you will eventually drop.
Usually week long breaks, or even longer are very beneficial, especially if your cock is appearing more and more beat up, or you start losing EQ. Normally these breaks are taken after 3 or more months of a regular PE routine, but if you make a mistake and go way overboard causing lots of damage, you should take a week off immediately to heal up and then start again at a more moderate force level.