pick up 2 50 pound weights, and then do the motion of drawing a bow. Your limit is the speed at which you can do that motion. So yes a very strong person could bow spam. (and trained archers are very strong people) the real limit is your stamina. because after you pull back that bow so many times you get worn out. pulling a 100 pound bow back 60 times is like doing 60 reps with a 50 pound weight on each hand. so is bow spamming possible yes, would you ever want to do it in real life? No because you could shoot off 60 arrows in 30 seconds and would be worn out. Possibly even shooting the last 20 arrows very inaccurately due to exhaustion. TL;DR Minecrafts bow mechanic is so different than in real life its hard to compare them, but yes you can shoot 1-3 arrows a second if you wanted to.