varies with each truck... mine was still able to hold steady at around 2800-2900 psi after 225k miles in my truck and the 20k before that with stage II injectors...
my new 17* HPOP can hold well over 3k psi at WOT now... my old HPOP was not in terrible shape but could've been in better shape.. if you can get a gauge to check HPOP pressure then hook it up, it should read anywhere between i'd say 600-800psi at idle once it's warmed up and at WOT it'll spike up over 3k then it'll settle, once it settles down is the psi that your HPOP is capable of holding and that's the number you want to read...
below 2400 is a terrible HPOP
2400-2800 is not so bad but recommended to change if going to bigger injectors...
2800-3k is in good shape and can support slightly larger injectors like stage Is or IIs, but will throw a CEL
3k+ your HPOP is in great shape and will support stage IIs and probably hybrids without throwing a CEL