thats a subjective question.. I use about 3 seasons as a guide, however if they puff they go too.. A123's for me last about 5 yrs. LioN batts seem to last 5+, I have some that are 8yr in smaller planes.. but in my jets never more than 5..

I am religious about checking my batteries.. I balance check and balance all of them except Lions. I also store charge them for sitting.. we often charge our turbine batts and then let them sit full.. not good..

I purchased a good charging system that will discharge quickly too, so I can put everything at storage charge quickly.

As far as TX goes, it depends too.. I have Jeti with ION battery, it should last a long time.. and its monitored. I used eneloop nickel packs in my spekky / JR stuff, and they lasted 5 yrs no problem.

so the answer... it depends.