We still co-sleep whenever my youngest needs it. He turned 3 in May. He slept in bed with DH and I until he was nearing 2, and now comes in whenever he wakes up or needs snuggles. Or if my oldest son has a sleepover, he's happy to give up his bed to sleep with us. I wasn't planning on getting him out and still letting him sleep in bed with us whenever he wanted. I was planning on buying an Arms Reach Co-Sleeper or making something like it, so baby can be on the outside and my toddler can be in the middle.
But although this is working for us now, I remember bed sharing every single night until he was almost 2 ish. He would marathon nurse. I couldn't get any sleep. He would push me (unknowingly) until I was clutching the sheets trying not to fall off. I hated every second of it. We just bought a fancy new frame for our bed, so there was no way we were going to size-up. I actually just transitioned him straight to a toddler bed into his brother's room. Now they have bunk beds (although we have always had a 3 bdrm house) and he sleeps on a twin. He's happy most nights in his bed, but sometimes he wants us. After we transitioned him into his own bed, he stopped night time nursing as much. He was literally JUST doing it out of easy access. I mean, sometimes it was 8x at night. I was a working mom at the time (working 10 hr shifts until 11pm) and it just wasn't ideal for us.
I was firm at first that he needed to start the night in his own bed. I would lay in there with him and run my fingers through his hair or rub his back to sleep, then sneak out when he drifted off. Of course if he woke up, I'd let him come in. Or if he was happy, I'd lay down in his bed until he fell asleep again. Now I'd say once a week MAYBE he comes in. I think because it's not "off limits", he doesn't "abuse" the right to mommy cuddle time. He also started sleeping better, too. I think gradual and with love is the key.
Edited to add: he also doesn't go to sleep on his own. Probably because I've always either nursed or rocked him to sleep. But to be honest, I don't really care. I'd rather him fall asleep with me rocking him and carry his 35lb butt to bed than sleep train him.