I bought an Icom in February 1991. I hadn't recharged it or used it since January 2008, when in June 2008 it took me 3.5 hours flying, from inside the Leeming MATZ to Fife to Inverness, following radio failure.
I regularly discharge it completely, then recharge it.
We now have a cig lighter socket in the plane, which Icom supply an adaptor for.