I use a failsafe switch on a regulator that regulates dual batteries, which are usually LIPOS btw. This then goes to a EQ10 which insures constant clean voltage to my servos and RX. Perfect combinaton that has never failed me.

Yes the TX battery can fail. If they offered a redundant source for that I would use it.

The key is reducing the amount of single source failure points. If you install all of the above items correctly they the odds are in your favor against a failure not for it.