My DC's co- sleep with me & DP quite a lot. I've never really thought much of it until someone I know was utterly scathing about kids sleeping in bed with parents, saying it was totally unhealthy. Our house is a bit like musical beds at times - DD 5 sleeps with me a lot and DS 9 will still want to come in maybe once a week. It seems to make them feel reassured and I always took the view that it won't last forever and they will grow out of it- which DS 9 is currently doing.
Aibu to worry about it? I just have always had a laid back view on it. Another friend said she lets her DS 10 still sleep with her occasionally if he wants to but it's rare.
The other woman who was scathing was very against it from all viewpoints saying it made kids dependent and was weird and unhealthy- I never thought it was weird and know lots of people whose kids still want to sleep in the bed with them.