all this online analysis of what is low enough in gear inches is so dependant on the amount of weight on bike (I used to have about 40lbs) and how steep and how long the hills are.
KD, only you and you alone can try some "steep" hills with teh weight you will actually be carrying/pulling and see if 24 gear inches is low enough--I personally would find that a minimum for really hilly areas, and 21-22 is more realistic for steep steep sections and or when you are bagged, or at teh end of the day and you've added 5-10lbs more of food on your bike etc etc.

but the only way is for you to try it. Remember though, beating the heck outta your knees will show up later in life (if you are young)