You can, but it's kinda hard on the tester to be constantly on and loaded.

I presume that Dragon Heart (good handle) is flying gas engine planes using ni-cads for the flight packs. If so, discarging, also known as cycling, only needs to be done periodically. Not constantly.

Over cycling a battery pack can be much more damaging that not cycling them at all. Too many heating cycles. A couple of times a year should be adaquate. Get a good battery charger/cycler that includes with it some way to monitor the charge/discharge times. This will give you a fair idea of the condition of your batteries as they age if you note the readings and compare them later.