My gut reaction is it's not worth using the old batteries. However, if you run them through several charge discharge cycles and they appear to have good capacity, go ahead and use them. If it were me, I'd replace them. Actually, it was me last May when I started flying again after being out of the hobby for a long time. I had 4 old transmitters that were not even narrow band. When I looked at the cost of new nicads and sending the transmitters in for narrow banding and to get them checked out, I just decided to go with a new radio. You can get an entirely new 4 channel radio system for about $100. Even better, if you can afford a bit more, is to spend another $50 or so and get a 6 channel computer radio.