What age for mid-sleeper bed?

[GiveMummyTheWhizzer]

Looking for real life opinions - google is contradictory and we don't have the original manufacturer guidance.

We are replacing our bed, which would make this a perfect time to give DS1 (11) our current bed and move DS2 (3, only just but size of a 4 year old easily!) from his cot bed with bed guard into DS1 current mid-sleeper.

DS2 sleeps nicely in current bed. I'm worried he is a little too young for a mid-sleeper. Real life thoughts/experience much appreciated.

He gets up and down into the mid-sleeper in DS1 room no problem - but has never slept in it.

Minor quandary in the grand scheme of things obviously but looking to recycle what we have rather than replace in a year or so. No room to store the mid-sleeper unfortunately.

DSC went into a mid-sleeper at 3.5 he has always slept in it fine.

Ds went straight from a cot into a mid sleeper at just over 2.
I thought that as there's a rail all the way around he wouldn't roll out so should be safe enough.
He can go up and down the ladder by himself when its light but in the dark he shouts for help or the light to be put on.

I think that mid sleepers generally say 'from 4 years'. It isn't about size but rather coordination.
If you are happy that your 3.5 year old can manage the steps when sleepy/wakes in the night then crack on. You know your child best!

Ps my eldest slept on a mattress under the mid sleeper for a while: it depends if yours is a void or made of drawers etc.

Thanks everyone. He's pretty clued up.

I could also use the existing bed guard to make the outside rail next to the sleeping end higher.

At 2, it was the same single he'd always had and came with add-on legs. It already had the railings. He had a nightlight so could see for the ladder. Gave him more floor space in a tiny bedroom as he could use the underneath as a den.