My question is How long the program can be followed?
You can potentially follow PTTP for years.
IMO, the keys to making it work sustainably over the long term are being patient and cooking your cycles in different ways.
Especially with high frequency deadlifting, I'm not an advocate of testing 1RM too often, or milking cycles completely dry before back cycling. Back cycle when you feel like you are getting close to a 5RM and keep patiently nudging up that comfortably hard set of 5/80-85% 1RM range (credit to Dan John for this piece of advice). I do think think it's worthwhile to periodically challenge yourself with weights that are a little more than comfortably heavy, but not necessarily real maxes, what Dan John calls a "PR without maxing." There's a skill to heavy attempts that is hard to develop if you challenge yourself TOO little.
I started out with linear cycles, and made good progress up to a point, but as the weights got heavier, I started to feel a little beaten up and stale.
For me, the biggest adjustment I made to keep feeling good and avoid plateaus was using 4 steps forward/3 steps back wave cycles, and using relatively larger jumps between the 4 sessions in a wave and smaller jumps between waves, such as 10-15lbs between sessions, but only 5-10lbs between the start of each wave (higher max = bigger jumps/lower max = smaller jumps -- measured in lbs, not percentage). This way you get a nice rhythm of easy, medium and challenging sessions, rather than a lot of easy sessions at the beginning and a death march of hard sessions at the end -- it's...wavy. With this approach, you can start a little lighter, say 65% 5RM, because each wave ramps up more quickly.
As I progressed, I often cut back frequency from 5 days/week to 4 days/week. This fit the rhythm of 4 session waves, but I don't think it matters if the training waves and the calendar week are out of synch.
Another approach is more of an "Even Easier Strength" step cycle approach. Cruise along with a constant top set weight at an easyish moderate weight, go a little heavier when you feel strong to gauge where you're at, and then reset your cruising weight accordingly. This also fits with the idea of nudging up your 80-85% 1RM over time (not necessarily lifting in that range all the time, but using that as your benchmark instead of a true 1RM -- just focus on slowly improving the level that is "comfortably heavy" without necessarily ever maxing).
I also much prefer the original 100%/90% scheme for the top and back off sets. The 90% back off set is lighter enough so it's physically and psychologically easy, but still heavy enough to add quality volume. The revised scheme, with a fixed weight for the day and sets of 5,3,2 reps, doesn't require any plate changing or calculation, but after a tough top set I really enjoy being able to take some weight off the bar. It also feels great to use a weight for an easy back off set that might have been a tough top set earlier in the cycle.