My son just turned two and he stopped using it a few months ago. We dont use a booster or anything... he prefers to sit at the table like everyone else!
Both of my 2 year olds and my 3 1/2 year old sit in their high chairs at every meal,however, our high chairs are the wooden stackable highchairs that you see restaurants. We took the front bar off, so all three of them can climb into their own seat, and sit nicely like in a big chair, its just a little taller and prevents them from having enough room in their chair to screw around during dinner.
We will continue to use them until they are too bit to comfortably sit in the high chair and they can sit nicely in a regular chair.
We probably put DS in a booster at aroun 18 months, but he used the high chair for breakfast and helping in the kitchen until just before 2 1/2
We never used one. I used a Bumbo with a tray until she was around 8 months old, then just let her sit with us, since we rarely eat in the dining room. We do still use a highchair most of the time when we go out, though-- she's currently almost 16 months old. That's mainly because of her height, though. She sits still while she's eating, so once she's tall enough to sit on the normal seat, we'll stop using the highchair.
my oldest two who are 4 1/2 and 3 now used theirs untill they were both 2 1/2 or so. my youngest is 18 months and still using it :]
I think my son stopped using his high chair somewhere between 20-24 months (he was a little big for it anyway and wanted to climb out of it) he now has his own childs folding table and chairs that he uses. we still use high chairs at restaurants though (he is 27 months)
Around 1. I tried booster seats for a while then went to a normal chair. He has done fine there since 18 months.