That is like saying you have a car that runs 2 minutes then stalls. There are many dozens of reasons that are possible candidates for trouble. It can be as simple as it needs cleaning. A proper cleaning is what we alway start with.
A proper cleaning consists of disassembly, cleaning, inspecting all the parts and then reassembly while checking the function as you go.
That is like saying to rebuild an engine because it will not start.
Most likely your problem is in the winding mechanism (i.e. keyless works or main spring barrel). I would open the case and observe the winding pinion, crown and rachet wheel for proper meshing as you wind. Another strong possibility is a problem with the rachet wheel "click" or "click spring" which could be allowing the main spring to unwind as soon as you finish winding. It is also possible the main spring is not properly situated in the barrel.
As Don says, it could be anything but these are possibilities you could start with. Hope this helps.
Both of you are posting with the intention of helping--and that's never a bad thing, IMHO.
If the cleaning/oiling history of the watch is not definitively known, then I think Don's analogy was "right on the money".
While a proper cleaning is a process that somewhat resembles an engine rebuild, a more realistic comparison would be to a tune-up--which, like watch cleaning, falls into the necessary maintainance category.
In the case of a watch, failing to do a timely cleaning can result in wearing-away of metal, shortening the life of the watch or leading to the need for more expensive repairs.
By the same token, had a cleaning been performed fairly recently, then it would be wasting the customer's money to suggest a cleaning, rather than simply focusing on diagnosis.
Popeye, if you want to do a little diagnosis for yourself, I believe that, if the problem lies with the click, clickspring, ratchet wheel or crown wheel, one wouldn't even need to pop-open the watch case in order to figure this out--at least in this case.
Since it's stopping within about 1/2 hour after a full wind----once the watch stopped, see if it requires many turns of the crown to fully wind it up or if the crown can only be turned a small amount. If you could fully wind it at this point, it would be apparent that the mainspring was unwinding prematurely.
A problem with the integrity of or positioning of the mainspring or barrel parts would show as a watch that could not be fully wound in the first place.
A relatively simple problem is that one of the hands could rubbing on the dial, crystal or another hand.
Beyond this, there are many internal causes for the same symptom, as both Don and Steve have said.
If I'm wrong, I'll gladly defer to those with watch repair expertise and trust that they will correct me.
What I need to learn to become an expert, far exceeds the amount of knowledge that I currently possess.
Hope this helps.