I don't have a specific standard. I pass all 1.5 year deer and most 2.5 year deer. We are lucky to have some land and neighbors who do the same,but wealso have neighbors who shoot anything that moves. We've been doing this even before AR's but have really seen the buck improve since AR's. Here is a buck I passed last year:
Here is the buck I shot this year:
Same buck? No way of really knowing. He was shot about 100 yards from where I passed him last year.
If you don't pass them they have zero chance of growing bigger. But I also don't criticize anyone if they want to shoot the first buck they see either. I did that for a lot of years too. As long as your satisfied after the hunt, that's all that matters.