We kept our son in until he was 3.5 ish. Kept the bar lowered in the day (so he could climb in and out, raised it at night. He was more than capable of climbing over, it just let him know he wasn't allowed to.
SO many mums have a 2nd baby at age 2 (of their older child) and need the crib... we didn't have a 2nd one coming, and kiddo *loved* his crib. It was his safe place, his timeout place. There was no reason to switch until he outgrew it.
Added benefit: By not switching until he was older (and just taking off one wall in order to ease into the transition) it was NO problem having him stay in bed at night. We had 2 or 3 nights where he got up out of bed. Since he was older it was pretty easy to explain to him that he needed to stay in.
It's practical to move an older child with an infant coming. But that doesn't mean it's necessary or "time" for a family that doesn't have a baby needing the crib.