NO but I take the time and get my crosshairs level with the stock. Once set up properly, I use the horizon/target and just be consistent.
The big one if using a pedestal front rest, is that this be level before shooting. otherwise, you will cant the rifle or the stock will be canted to fit the bag. Worse, the rifle will torque during recoil to fit the canted bag and you will start launching bullets inconsistently.
With a level scope/rifle/stock, the only thing to do is set up your rests to be level and you will always know you are good to go.
If shooting with a sling or bipod, I still would have a level crosshair. you don't always have the time to look at a bubble level and even if you do, you can shift when you go back to your sights/scope. You eye/body wants to level that crosshair for better or worse.
Make the rifle fit you in the position you are shooting in, then make the sights work for that position. Your firing position should feel very natural and if so, you will always be level.
Jerry