Here is my tale. DS3 SCREAMED to the point of making himself sick every single time I put him in his crib, or his cot. So we ended up sort of cosleeping, and me getting more and more sleep deprived until at 16mo, I took the sides off his cotbed and turned it into a 'bed'.
He has since slept quite happily in there. He is now almost 20mo. I had to put him in a playpen whilst doing some DIY the other day. And he started screaming "no shut, no shut, me shut in, me stuck"
He also yesterday had a screaming tantrum in a lift, as soon as the doors shut.
I have discovered that he REALLY doesn't like feeling 'shut in'.
I think he may have a touch of claustrophobia. But he has been like this since the day he was born, and has only just had the vocabulary to tell me why he doesn't like it.
I'm glad I didn't ever press too hard with him sleeping in his own crib, by the sounds of it, to him, it would have been the equivalent of getting me to try to sleep in a spider infested cave!
I have coslept with all 4 of my DC's, for varying lengths of time, as I can't bear to let them CIO.
One thing I can tell you, after 14 years of bringing up children, is that none of them will be cosleeping at 5yo!
There is a limit to it - and you DO miss the closeness and cuddles once you don't get them any more.
I would examine what is more important to you - your own bed back right NOW, or disturbed sleep with a crying baby who doesn't want to yet be parted from their mum.
Also, the first wave of separation anxiety hits right around 8mo, when they realise that they aren't a part of mummy, and they don't like it when she's gone.
I find there's about 3 'waves' of separation anxiety - from about 8mo-12mo, from about 20mo-26mo, and from 3yo-3.3yo.
My best suggestion? Now might not be the best time to attempt it, and just embrace the night time cuddles for a little while longer.
But I'm a softy that believes that babies cry for a reason, it's their only form of communication, and when they cry, they are trying to communicate something to you...