OK, found this in Active. I had shared care with my Ex-H for my DS1 (long story about why it's not happening right now, to do with Ex-H's partner hurting DS1, but it worked for 8 years, so bear with me!).
We had a 60/40 split to start with, then a 45/55 split. It worked really well to start with, until my Ex-H got with a new partner and started a family. Continued it for years even in the face of her hostility, DS1 enjoyed spending so much time with his dad, and I got used to it.
We started shared care when DS1 was two, and it went on until 6 weeks ago, DS1 is now 10. Hopefully we can get back to a shared care arrangement at some point, but that is dependant on Ex-H's partner dealing with her serious anger issues. It has NOTHING to do with Ex-H's ability to care for his son or be a good dad, and everything to do with the fact that his partner hates the fact that I exist and my Ex-H has a past, and takes that out on DS1.
I'm not going to say it was easy to spend that first Christmas away from DS1, it wasn't, I spent half of it in the bathroom in tears, and the other half plastering a false smile on my face for the sake of my other DC's (DS1 was 3yo when he first spent Christmas away from me).
BUT I learnt to cope with it because I knew that if I felt like that when I was away from my DS1, then so did his father.