When to move to big bed?

Not thinking of doing this as yet but with #2 now on the way, ive been thinking about whether we will need another cot, or if she will be in a bed by then (she will be 21 months when baby is due).
I am able to get a second cot off my sister so this would be no issue, and also will be using a bassinet for the first few months with #2.
So what age you moved your toddler to a 'big bed' and/or what age would you recommend?
Thanks

We moved DS to a big bed at 15months, he is in there alone for day sleeps and I co-sleep at night. We hd no issues at all. He doesn't climb out of bed unless I'm in there with him for some reason.
A few of my coffee group have moved their babies already too with no problems.

My son started sleeping in a bed around his 2nd birthday. He didn't mind going to sleep there but I gave up on it after a couple of months as he didn't sleep well. He would fall out of bed about 4 times a night (the bed was really low to the ground for safety but guard rails would also have helped). He would kick his blankets off and wake up cold. And he would come in to my bed about 1am. We have been co-sleeping since birth though, so I'm guessing the cot-to-bed transition would be a bit easier.

Lol i cant remember exactly....but i think Jade was around 17/18months old, & we just made a big deal about wot a big girl she was, & how special her new bed 'big girl' bed was, & she was fine, we started off by taking the side off her cot so it was 2 much different.

I'll have 26 months between our two. I intend to have DD1 in her cot for as long as possible, she's small for her age and a wriggler. If she decides she wants to she can go earlier though. I had a friend who moved her dd at 18 months and she reckons it was hard and wishes she'd kept her in the cot.

Baby will sleep in moses basket for the first little while. If need to I will get another cot.

I think it would be easier on you to move her and get her adjusted to the big bed before bubs arrives. Some kids take longer to adjust than others. I moved my two into big beds on their second birthday but truthfully I could have done it sooner. I was just scared to do it lol.

hmmm whats the longest you would keep a child in a cot for ? my daughter will be 2 in july and i just know that the second she goes into a bed she will keep getting up and try get out of her room , try open her window etc etc , she is a runner and very adventerous and a bit naughty  so even tho i was thinking about buying her a bed for her 2nd birthday i am now thinking i might put it off a bit longer if i can .