I use a fixed mag 35x scope so I have to do everything on 35x. Before that I had a big Nikko mark 1 and I found that the optical quality at 50x was inferior to 40x or 45x so I used that at around 40x most of the time.
Shooting at a high mag takes some getting used to, but I find the optical quality of a fixed focal length scope is so much better than the zooms that I could afford, it's worth the effort.
Arguably you should reduce the mag so that you can see more of the surrounding area and get a last-second update on what the wind is doing, but there are some far better shots than me who are successful on a fixed mag.
At least with a fixed mag there can't be any image shift, except when focussing.