I used to keep track of my case usage (as best I could). That lasted about two months...
The thing is that unless you start with your own new brass, you'll never know how many times it was previously loaded anyway. A lot of the "new" brass I've reloaded the very first time might have been loaded a dozen times previously. If you shoot a lot (as I do for organized 2 times a week IPSC practices), I'd spend more time sorting than I would shooting. Then you have to get the rest of the guys to sort their share of brass to remove your cases. It just ain't feasible for me.
I also don't see much value in keeping track. I just watch out for bad cases - usually split case mouth or loose primer pockets. I don't find many like that. And with my IPSC buddies, we've probably reloaded a portion of each others' brass 50 times!