Futaba and Lipo's
I have been using Value Hobbies 3S in my 10C for over 3 years without any issues at all. I fly until mine hits 11-11.1V and then recharge. Good for another 2-3 months of flying for me. My buddy and many others at our field also use them without any signs of problems. Now having said that a good friend of mine that I have known for 34 years decided to buy one for his Futaba 6EX and he used it a few times without any issues but then all of a sudden he had 3 airplanes go into lockout and they flew away, all within or < 5 minutes of taking to the air. These were all different receivers/equipment and planes. Lucky he had one he found that went into a corn field with no damage. This was 2.4 by the way. I was told by another friend that has flown Futaba forever that the 6EX radios do not like the high voltages that are maintained by using the 3S lipos. I know people using them in 7C,8series,9C,10C,12 and 14's though with no issues.
Mine usually charges up to 12.2V but as someone else above stated it drops quickly down to 11.7-11.8 and usual stays there for a long time.
Oh I also charge mine out of the radio and keep a fully charged one in my transmitter box ready to go just in case I do hit that 11v mark while at the field.