Check out this site:
http://www.regrowth.com/hair_loss_conferences/american_academy_dermatology/1998/aad_1.cfm
It suggests that not only will using 5% once a day eventually match the results that you would see using it twice a day, but also using 5% eventually matches the results that you would see using 2%. But I heard elsewhere that 5% grows more than 2%. I heard that the higher the dosage, the more growth you will see. I tend to believe this over what this site says. Using 2% is an alternative to those who experience unbearable irritation with use of the 5%. But definitely using 5% once a day vs. twice a day is okay. I think it will just take a few more months to see the same results.
SO, to sum up, use 5% once a day if you can't use it twice, and if you experience irritation that you can't handle, use 2%.
As for dependence, my analogy is this: When you get your drivers license, do you tell yourself that you don't want to start driving a car, because once you start you will never want to go back to riding your bike? Same thing with minoxidil- it helps regrow and maintain hair for us experiencing male pattern baldness. As such, minoxidil is a convenience, like having a car. You COULD ride your bike to work, but why not drive? You COULD succumb to male pattern baldness, but why not battle it with minoxidil?
Sorry for the lame analogy, but seriously, I didn't want to be dependent on it either, but once you start, it is simply NO BIG DEAL.
Just my 2 cents. Good luck.