s/o booster seats - when to take off the high-back?

[ringstrue]

Anyone know the recommendation for when to take off the high-back of the booster seat? I hate how hard it is to find this stuff online. 

[penguingrrl]

I will add to fivedogs that my 5 year old goes back and forth between a high back and a backless. She stays put without the physical reminder that the high back provides and says that the high back is less comfortable than the vehicle seat (and that makes sense since it's plastic and far less cushioned).

For long drives and/or at night both of my girls (almost 8 and almost 6) use high backs because the headwings make great pillows and help keep them up while sleeping. During the day for just around town they usually just want the backless. My car has side curtain airbags and they sit correctly and the shoulder belt fits correctly, so I'm comfortable with that.

[lindsaymg]

My almost 7yo is in a backless booster (clek olli).

[mrsGreeko]

We moved my oldest to a backless right before she turned 8. The back wasn't comfortable for her and he belt placement didn't seem as good with the back on.