Is 22 months too young to learn to use the toilet?

[bronya]

DS is potty trained, and is reliable. Is he too young/small to use a training seat on the toilet with step/ladder? If so, at what age could we start? I don't want to set him up to fail! Also, can we continue to use the potty when out and about (e.g. picnics etc) if he needs to go, or do you have to change over completely to only using the toilet (and if so, what do you do at friends' houses - take a training seat with you?).

My dd started using the toilet at that age. We used a training seat and step stool at home and I just held her on the loo if we were out somewhere. She still used the potty from time to time if she preferred and had no problem switching between the two. No way was I lugging a training seat or potty around with me while heavily pregnant and with two kids under 3 so she just went in the grass or behind a tree or whatever if we were on a picnic or similar.

DD switches between her potty and the loo (has a step and little seat) as she chooses. I'm noticing that the taller she gets, the more she uses the loo.