Yeah, we don't have huge problems with mirage for the most part. The air out here is very dry so that mitigates it a lot.We have a 1000 yd range not too far from where I live here in Florida.
I am not one of them but there is a very dedicated group of long distance shooters. They take it very seriously.
They also only shoot early in the morning but it is not necessary because of the wind. We don't have the wind here like they do out west (except when a hurricane hits). The main problem they deal with is the mirage. After about 10:30 or so when it heats up the mirage is a deal breaker.
Our longest range is 3500 yards. It is out in the Blackrock desert. That is usually a weekend of shooting because it is a three hour drive to the range.
So we set up a nice camp and spend the day shooting and experimenting, and enjoy BBQ and sampling whiskey during the night.