This certainly sounds as a stupid question and the answer will be: It depends. It depends on the type of watch, the condition it is in, the spring etc. So I must be a bit more specific.
Although I am usually not in for wrist watches and pocket watches instead, this forum has infected me to some extend. I got some Gotham, Elgin, Bulova, Wittnauer, Gruen, Waltham (that sort), all made around 1940 to 1950 and the regular, mid-priced type of the time. I also like these watches, because even a dummy watchmaker can take off the back and get the movement out, in order to clean the case.
I carefully selected what I've bought and from whom (expert dealers), and wanted them in good running condition, with some information indicating to me that the seller had a clue what he was talking about. Some of them went straight to the watchmaker, if I knew of some defects other than with the movement (glass broken etc.).
So, in order to come to the point: Is it within the normal range, that a wrist watch of that type and year of production runs only 18 - 19 hours, thereby keeping time fairly accurately until it stops? For a pocket watch, that would be way too short. I also noted that, without having it serviced, letting the watch run through a couple of times, I gained some 30 minutes in total running time, probably after loosening dried-in oil.
The first two of them have gotten their new wristband.