my local plumber (installs well pumps and full water systems) says that as long as the shut down (drain down)time is longer than the recharge time (pump running) then its perfectly okay as long as the tank is sized correctly or larger for the pump volume or the needs of the home. The reason the pressure tanks are used is to prevent the non stop pump cycling due to instant pressure loss in the plumbing system if you were not to have the resivoir.
My plumber also said that typically the size of tank I am using is used in on chicken and turkey farm applicatons in the area due to needing higher draw volumes for the automatic waters durring the hot periods of the summer keeping the pump from cycling to much. He also said that the main reason he recomended the size of tank for me in my rual country home is because of hydro loss. We have enough of a water reserve to last a good day (only using water when absoluty needed) with that pressure tank instead of having a small tank where I would need to fire up the generator.
I just think that if the amount of water is even half of what your well pump is capable of putting out, that there is major money to be saved and keeps that $$$ right into your pocket at the end of the day
