My workouts only last about 90 mins, and unless I'm towards the end of my contest prep and really need to scale back numbers from everywhere, I actually try to keep 3 scoops of ANACONDA on heavy days (the very 1st suggested protocol, which I feel has worked well for me). Even 'elite' athletes don't really train for 2-3 hours. I would imagine that the suggested serving recommendations were made for an average gym rat (175-195 lbs...?) who busts his ass for at least an hour per session.
Remember also that the recommendation is taking into account how much Beta Alanine you want to get, so unless you're one of the few people who react poorly to it, you probably want to stick to 2 if you can (although I've seen some people only use one, but throw in a few scoops of MAG-10 to 'balance it out')