Man, I'm looking at a dude who just made two pr's in a session with good form. To me, that dude, even if he needs 5 minutes in between could probably drop back down to a bit above 90 and do another couple.
NO, there is no rule that says you can only do 3 or 4 singles. You just have to plan out a cycle sort of like I describe in my other post. The way I do it would sort of be a high, med, very high, low kinda thing where you drop the numbers up and down as the intenstiy increases to allow for recovery.
BTW, I wasn't implying that you weren't using good form for those singles. I know that wasn't clear. I was reacting to your plan for next time. Singles are maybe 70 or 80% planning and the rest is thinkng and reacting on your feet. So basically you wait until you get near the max range you previously hit before you ultimately decide what is going to happen. And a pr is not necessary every time but you will find it to be very powerful at first so you are bound to see some PR's. But usually the BIG PR is saved for after a run of single where you backoff for some recovery and then do a test if you want. You of course don't have to as you will have a very good idea of where you stand and can plan things out from there. After all, the "tests" are sort of built it.
Dealifts can be very difficult for some to do more than 4 to 5 singles at most on. Im my experience I can do a bunch on week one, etc. but I am not going to tell you that you can. So they are not the best example. But read what I wrote before about how you can plan out a cycle based on your ability. Also, you can build up more work capacity on them later on as you go.
What you gotta think about is that a PR is great but just hitting one or two singles, even a max doesn't do much to cement any strength gains. The relative max can be very fleeting in that way. That is why you plan it out so that you are accumulating a lot of work ("a lot" being a very relative term!) in this heavy range over a period of several weeks.
I have about 4 different ways to run singles. This is just one of them.