It's tough to comment on how long they last, because it's going to depend on how often you play. So I started proxying 4 years ago and haven't had any problems yet, but I also sleeve them as though they were genuine, and only play maybe one game a week.

As for avoiding overpowered decks, I've been playing with the same group of guys for nearly 25 years. We've worked out where we like to be, and self-balance for fun. It helps that I'm a total Johnny, so I can whiff a game completely and still have fun as long as I "did the thing."

If you're just asking how to avoid overpowered decks just because of the ability to print proxies, people with big budgets (or a long history of playing) can get all those actual cards already and there's banned and restricted lists for each format (and the formats themselves also help, as they limit which sets are legal, so standard doesn't have to worry about interactions between new cards and every single card made in history).

And for more casual games (that ignore ban lists or allow custom cards), there's the whole dynamic of "if I always play my deck that just stomps everyone by turn 2, eventually no one will want to play with me, other than to throw their overpowered decks at it, so I'll save the extreme ones for special occasions".