I can see only two ways you would make it 5 out of 8 years in my area. One is to be on several teams and go with different teams. I once had a player who captained six teams a week, all with different rosters. He went several times over a twenty-something-year period, but never with the same roster. His trick was finding who he thought was the best player in his divisions and putting them on his team, then filling out the roster with people he thought that player could coach up during a time out. Sometimes it worked, sometimes it didn't. His teams never did well in Vegas, having their fair share of the 25% two-and-outs.
The other way is to turn your roster over every year. I once had a couple (a 5 and a super 7) who did that. They put brand new players on their roster every summer and didn't coach them at all. No rules say that you have to coach or that you have to improve. Around the middle of Spring, they started coaching, knowing the system is a system of measurement that allows you to play matches as you improve before raising your skill level. By the end of Spring, some of their players had gone up but you never know when or how much improvement there will be. Through the tournaments, more players went up. They never sandbagged a single skill level but managed to time the improvement and get to Vegas three years in a row. No sandbagging, just the realization that the player who is improving to the next level gets to shoot that level a couple of times before going up. I see nothing wrong with that, it happens that way for everyone. It's unpredictable, but they managed to do it three years in a row. I don't know how many teams utilize that method, but it could explain why you see players who look like they're better than their number in Vegas. They qualify, then start practicing and taking lessons during the two months leading up to the event, and the improvement is just hitting the books then. Just because someone is shooting better than their number, it doesn't necessarily mean they're cheating or that they need to be punished instead of rewarded. The reverse is also true - APA has disqualified teams before even though they didn't think that team was cheating. There's a certain amount of improvement they will accept as normal but too much can get you disqualified. In those cases I think they relax the usual two-year suspension that comes along with disqualification. It's similar to golf tournaments where you get disqualified for shooting a round three or more strokes below your handicap - it's possible, but statistically improbable.
Aside from that, I can't think of a way a roster would make it a couple of times before I decided they were way outside the norm of the approximate one in 30 odds. Individual players may do it, but not whole rosters. Local oversight helps that, something it sounds like your area was lacking. Again, I think it's probably win/win that you don't play APA leagues any more. Good luck playing in a league where you don't feel the temptation to cheat, as you clearly don't seem to be able resist that temptation.