Well, I'm recovering from a shoulder injury, but I went from 20 wall push ups to 40 in one set, 30 sec hand/knee plank to 90 sec, 25 wall squats to 50 in one set.
It's taken me a few weeks but I feel like a couple more will see me doing knee push-ups (hopefully). And this is with once or twice a week.
I know Mark noted in the PBF eBook that when you do "level up", maybe stay at the previous level a session or two longer just to ensure you're ready to progress.
Example being this past Monday. Did 60 wall push ups. But I tried knee push-ups Wednesday. Definitely not ready.
Anyways, to answer your question. As long as you're experiencing some gains, feel good, and are having fun, I'm sure it's okay to go at your own pace. That's why PBF is meant to be adaptable to any fitness level.