Britax Elite question

[brachy]

My DD (age 5.5yrs) is harnessed in a Britax Elite (not the TWE). I have just moved the straps onto the last notch. At what point does she outgrow this seat?
Should her head be level with the top of the seat or can we let her get to eye level? She is well within the max weight of the seat (25kgs) as she is 16kgs now.
I'd rather keep her in this seat for as long as possible.
Many thanks

ff it's when the ears are at the top of the seat afaik. if you email britax they will send you the instructions or they were very helpful when i called them about the rf seats.

:)