I've also got minimum 20k rounds through Gen 2 and some Gen 1's though actually it might be closer to 40k. Many many dozens of cases and about a dozen classes. I've left them fully loaded as long as two or three years. I never use the covers. They always work fine.
My piles of gen 2 and gen 1 magpuls are boring because I'm looking for excuses to replace them with Gen 3s but...so far I have never had one fail to work. I have no doubt some have gone bad for other people but so did the old GI mags. I have gen 3's but I use them interchangeably with all the rest.
The only caveat as mentioned above is that some of the old straight 20 round magpuls were wonky. I like the way they look but I have also had the swelling issue. Sometimes they won't work in certain lowers. Never with the 30 rounders though.
All the guys I know who hunt bad dudes for a living (for our country overseas) run magpul mags. Maybe they've upgraded to the gen 3, but they tend not to replace things that work.
All of which is to say...buy the Gen 2s or Gen 3s but other than internet types I highly doubt you'll find anyone who runs them a hard who will really have an opinion about a difference, other than maybe the way they fit in your pouches.
