mkowske, welcome to the forum!
It sounds like you're already a strong climber. There gets to be a point where getting stronger becomes more and more of a challenge. At a certain point it's likely that you'll need to focus on intensity in order to see continued strength progression -- and yes, generally speaking, as intensity increases more rest time is required between workouts.
First off though, go climbing as often as you can. If you're projecting at your limit (trying to get to that 5.12 level) then you'll be exerting maximal effort for sure, and it'll be just as good (or better) than any home workout. Trying to climb hard lines will always be the most fun and most effective way to become a better climber.
As for training though... are you progressing with your current routine? As Clymb said, if you're already progressing then just keep it up! If not, then what do you consider your weak link? What's keeping you from sending 5.12 right now? If you want to train as effectively as possible, I'd suggest identifying exactly where you need to improve, working out toward that end very specifically, having a few different workouts that you can rotate to keep things fresh, and focusing on intensity (pushing your limits). If your workouts are significantly intense then you probably won't be doing them 4x a week like you are now (unless you're doing some sort of crazy endurance training or something).
Oh, and as for going to failure... I haven't looked into PBF but from what I understand it's a very effective program for general fitness. This discussion however is about training to break through very specific strength plateaus. I think there's a difference. When it comes to climbing, training to absolute failure has always been an effective method -- that's literally what projecting is after all!
Good luck.
