That's a tough one,It depends how much you love your plane. One thing you could do is,Put new batteries in.Turn transmitter on,check every hour or so,and check responsiveness on your servos , and check your batt,meter on your Tx. When the meter on your Tx.is way down ((,Don't wait till compleatly dead)).This will give you some kind of idea of what to expect. Example---If your Tx. batts. Are down in the ((Yellow-Red zone)) after say,12 hrs,Then you could probably get at least 6-8 flights out of them.((Maybe more,maybe less. I'm only Guessing,This is the only thing I could come up with.