I don't that much. Most boxers kickboxers etc. Don't bother that much. Generally considered not with the effort.
I aim to be ambidextrous so that I don't limit myself too much but I usually favor the right back stance (right leg back) but will switch stance often when sparring. My choice of stance will depend on how my opponent is standing, what block, strike or kick or grappling technique I want to do, whether I want to be defensive or offensive etc. For example if both my opponent and me are in a right back stance and I want to do a turning kick, I will usually kick towards his blind side, which in this case for a rear leg kick would be my right leg, so it is harder for him to see my kick. If I want the kick to be a bit quicker I might change stance and kick with my front (right) leg or just do a hook kick (which is always easier with the front leg than the back leg) with the front leg (left leg in left back stance) instead. Most of my kicks and hand techniques are about the same with either side except for a few like the ones I mentioned earlier. In a self defence situation there might not be time to switch stance to a more favorable one so I might be stuck with whatever stance I am in at the time so it pays to be good with both sides whenever possible.