My DD will be 7 in 3 months, and she too is still harnessed in a Radian. I recently just removed the cover to tighten the headwings so they'd stop falling down. She never complained about it, and they never fell on her shoulders, but they seemed to keep falling a little lower than where they should be. Tightening them seems to have helped! My DD sits in a booster just fine, but she's harnessed right now because 1) I'm too cheap to buy a seat when she has one that works perfectly well 2) The higher end boosters I want seem very heavy, and I can't LATCH in my off-center LATCH hooks. LATCHing is non-negotiable to me with the heavier boosters and being in the center is non-negotiable. I'm hoping to get a new car in 1-2 years (not for this reason LOL our car is on the outs..very old!) and hopefully it will have better LATCH in center or side airbags so I'll feel better about putting her on the side
So she may be harnessed until 9 (her Radian was manf. Jan 2010 and her 9th birthday is Jan 2018.. right when it expires! lol).
I do sort of worry about head loads, and also more obscure things like what if the car was on fire or sinking in water , I can't get her out as fast of a 5 point as a seatbelt. Also she can't get herself out a 5 point harness, so I worry what if I was knocked unconscious, she'd be stuck in her seat for whatever reason, and that makes me uncomfortable. BUT.. there's good and bad with everything.. always something to worry about!! She's perfectly safe in a harness or booster, that I know