NiCads are probably the most dependable type of battery for our use as they will put up with more improper usage than any of the others. They do have a lifetime though as all things do, NICads are typically good for 1000 charge/recharge cyles (twice as good as NiMh). One way to ruin them though is to reverse charge them and that is what is likely to happen if you discharge your battery by just turning on the transmitter and leaving it until the battery is down. The weakest cell will most probably get a reverse charge doing that and will probably be permanently damaged. The other thing that will ruin them is to fast a charge or a fast charge that is left on to long. If you detect any fluid or swelling , pitch the battery, it is no longer going to be able to function to full capacity even if the voltage measures okay. The fluid is basic (not an acid) but is still corrosive. If there is fluid, the seal at the positive end has been compromised and is non repairable. A leaky NiCad will also contribute to the dreaded Black Wire Disease in your electonics so clean up any leakage ASAP. The advice above to never run your tranmitter with the antenna collapsed for any length of time is very valid. The SWR (standing wave ratio) goes way up and the energy normally transmitted as RF is now converted to heat in the final of your transmitter. This will definately shorten the lifetime of your transmitter and could possible cause an instantaneous failure.