Granted its not the best way of discharging your battery in the TX but, there will be no real harm done to your tx. Thing to watch out is done leave the TX on when the antenna collapsed. That could cause some adverse effects to your transmitter. What happens is that the RF module in the TX will start to heat up becuase there is a differant load on it (antenna down) which could cause it to fail. Granted its very rare and it does have to be on for a LONG time. Most of the newer transmitters it wont effect it too much but it does vary from manufactor.