Well if you’re warming up and stretching it’s not really an “off” day. The point of an off day is a day off to rest. If you find that you’re responding well to the workouts, you can continue to add stretches and jelqing time slowly and gradually transition to less rest days. It’s not written in stone that you need any rest days at all, but as a beginner it’s probably better to err on the side of caution and start with more rest days than fewer. Although it’s tempting to feel like you’re wasting a day when you could be PE’ing, it’s good to think of those rest days as a valuable “addition” to the routine, not a “day off”, especially when you’re just starting out. Everyone’s different, part of the benefit of the newbie routine with rest days is to get conditioned and start learning how your body reacts to the new stresses being placed upon it.
I think the easiest answer for how long to stay on the newbie routine is at least a minimum of 3 consistent, dedicated months. Keep going after that time until the gains stop completely or until the workout time (that you’ve gradually increased to) has reached a point of diminishing returns.
Also, keep in mind that “more advanced” doesn’t necessarily translate into “more effective” and don’t be in too much of a hurry to jump into more complicated, expensive or risky routines. It’s quite possible you may be one of those lucky ones that are able to keep gaining with just the basic, light routines with lots of rest days.