I use the terms "run time" and "cycles", as these phrases are used in the radio control world where batteries are an integral part of how the vehicles run.
Run time means how long a single charge will last. Of course this can vary for each application, and how the user uses the battery. Are you running full auto, and can barely take your finger off the trigger, or do you fire in semi and only when you know it is a target you can hit? Right there, two people using the same battery would have very different run times.
Cycles means how many times can you charge/discharge the battery. If a nimh battery says it should be able to get about 100 cycles, then you can expect to charge it and then use it (one cycle), about 100 times.
Does that make sense? So, let us know what this will be used in, how you plan on using it, and with all that, we still won't be able to give you a hard answer. My suggestion is to not worry about run time. Carry enough battery with you to play a full day and then some, and you will never run out. Or, go lipo and it will never be an issue. Wait, being 15 you may want to stay with nimh for a while, because lipos can be dangerous in the wrong hands.
