It all depends on what you want done. I also sell fans like eqdizzle (great guy btw). I started selling fan setups because I hated changing 14 thousand batteries every time I trooped. With my setup you could have one battery easily power two fans and your helmet servo. It's also lighter than using 8 AA batteries.
I've trooped in my Fett easily 50+ times. Never once have I ever been concerned with my bucket blowing off lol, but to be fair I would never troop in rain or windy conditions.
Hearing issues are completely situational. I have my own hearing system that I use that is powered off my battery system (I have my chest lights, fans, servo, and hearing system work off one battery...this eliminated 19 AA batteries for me), however I really only use it at large scale cons (say Celebration for instance) where directional listening is quite important. Otherwise, when trooping there are others around you (squires or handlers depending on your groups terminology) which can easily point you directions to someone calling out for you.
Sorry for the delayed response but I just got back from vacation.