I like to have a follower that will be fruiting ideally no longer than two months after I harvest the bunch from the mother plant, unless winter is coming, but I can't really 100% achieve that.
So if my plants are going to achieve a height of 10 feet, I like to leave a pup when the mother is about five feet tall. Roughly by the time the mother fruits the pup will be about six- seven feet tall (maybe more, the pups grow faster than the original mother)
the fruit takes roughly four months to ripen the fruit, so by that time the pup is very close to fruiting. I also allow a pup to grow about every couple months.
Then when the pup is about five foot or so tall, I leave another one. I also only leave the vigorous ones. It will be obvious which ones are healthy and which aren't.
Forum member Greenie (Rene) told me that digging pups harms your mother plant, which makes sense. It creates a wound, into which rot, grubs, bacteria, ECT enter into the wound causing stress. If your plant is already experiencing stress, ie, standing water, flowering, cold, insects (nematodes on roots, aphids, ECT), it could cause your plant to die. That makes your plant kind of take energy away from growing to heal the spot.
Greenie told me that he recommends cutting unwanted pups off below the soil every couple weeks, adding energy into the rest. It also probably strengthings the plant. The roots from pups that are cut below the soil pulls in nutrients from the soil and adds it to the "pot" of energy the plant possesses/draws from. If they were removed, those roots would no longer be helping the plant. Hope this lengthy response helps!