That sounds about right from what I have heard. However, in any case, getting a pressing done when the stamper is not as worn is better. That is easier said than done, since the pressings from a stamper all have the same markings in the dead wax (inner groove area). Unless the manufacturer actually marks the record label in order of the pressing, I think it is about impossible to tell the difference. There are some limited releases that have a small number of copies made with a stamper, before it is changed. However, that makes them more expensive. I definitely have some records which are individually marked - like lithographs, but it isn't clear that the sequence actually represents the order of the pressing. I also have a fair number of test pressings, which should definitely be very early in a run. Decca uses a pink, hand written label for there test pressings.
There is one case with records with different markings from the same stamper. That is Decca and London records (only differentiated by the two labels). I have a personal theory about Decca and London pressings with identical stamper numbers. The Decca label (for UK consumption) was used for a smaller number of copies than the London label (used for US consumption). My guess is that first, the Decca plant at New Malden, which did the pressing, put the same type of label (Decca or London) on the first part of the run of records from one stamper, and then switched labels for the second part of the run. I think it is very likely that the Deccas came first (smaller numbers and for local consumption), and the Londons came second. This comes from my experience with listening to several Decca and London recordings for which I have multiple copies from the same stamper. The Decca labels always seem to be better, or at worst the same as the London labels. That would be true if the Deccas came first and one was comparing a recording pressed early in a run with a record pressed late in a run when the stamper was more worn. If the two records were both pressed near the switch over point, they would sound about the same. Anyway - it is my theory - I haven't met any Decca veterans of the New Malden pressing plant.
Larry