You still shouldn't run through a new pad that fast. How many miles did you put on your bike in that time? Of course, when braking, you should just add your rear brake to the front brake, when you need to slow down just that bit faster (in a shorter distance). I apply mine based on the situation, but use front brake as primary...
However, if your pad is worn down again, I'd be curious as to whether it was put in properly. You could have been wearing it down just by riding if the caliper wasn't set right. Your pad shouldn't be touching the rotor when the brake is not engaged, if it is, you'll be wearing it out in no time.