This is part of the conspiracy theory, that a 60 year old could not sustain 10 minutes of fire with an automatic weapon. It's really not a big deal to take 10 heavy suitcases up to your room in a hotel by yourself. Especially if they roll. Just take your time, space it out, take breaks, and if they roll... well... just roll it. You can also get a luggage cart without a bellboy.
In terms of sustaining fire for 10 minutes, I think it's important to keep in mind that this guy was completing something he'd been planning for a long time, and was probably so pumped full of adrenaline for what he knew would most likely be the last moments in his life (even if he held out hope for an escape), he probably didn't even notice.