"Can you give me a rough estimate?" OK. Between 5 and 25. Done correctly we can load it until it fails, usually a split neck which is harmless to all but accuracy.
The reasons are several. Most important are how well your chamber and die match in size, if they are close the brass will last much longer. If your die is made to minimum tolerance and your chamber is at max then the brass is worked pretty heavy each time. In this case, your brass will likely fail due to a split in the body which is usually safe but interesting. Smoke flies! Using neck sizers will extend the life of your brass because the body isn't being worked each time.
If your chamber is long and your FL die is short and you adjust your die to touch the shell holder each time and you load hot, your cases will stretch a lot each time and eventually seperate at the web. That's BAD NEWS! On the other hand, if you carefully adjust your size die to only set the shoulder back enough to barely allow the action to close on a reload then the brass will last much longer. And lighter loads will help too.
The most common case failures, for most of us, are split necks. Annealing (properly) can keep the necks safe almost indefinately but done wrong it can damage cases immediately. A Lee collet neck sizer die works the brass less than conventional neck sizers so case life is further improved with that die.
Now you can understand that anyone trying to sound like an authority by telling you the "average" case life is just blowing smoke, it depends on variables we can't appraise over the web.
It depends on your specific tools and rifle and the care you take in working more than anything else.
