I have been building AR's for some time and have learned a ton about the design know what works and what doesn't. I have 3 AR-15 rifles right now and all serve different purposes.

For someone to say you will get bored of your AR and it is an unreliable gun after 1000 rounds is BS. Unless something is wrong with your gun it will shot accurately and reliably for thousands of rounds. The thing that is so great about the AR is that it can be fully customized. If you get sick of the configuration you have, by all means change it. New barrel, stock, trigger assembly, gas block, free float tube, sights, or whatever can all be changed within a matter of minutes.

I agree for your first AR get one from a reputable manufacturer. DO NOT BUY ONE AT A GUN SHOW unless you know what to look for. There are far too many "part guns" out there.