I've done 50/50 with my ex since I moved out nearly 4 years ago. Initially it was really hard to be away from them but I soon appreciated the time off and space to rest in preparation for the next time they came back. We have a two week schedule with swaps every two or three days. They both have fully equipped bedrooms in both homes and really only need to bring things between such as ipads or specific toys they want for the weekend. Eldest DS13 is getting more into certain items of clothing and will come and get a pair of jeans or similar if he wants to go out. Our houses are 2 mins walk apart which helps enormously.
My ex and I co-parent fairly well, we try and attend parents evenings together and otherwise update each other on the kids needs etc.
I have discussed the possiblity of changing to week on, week off with eldest son but he prefers to stick as it is for now.
I have a new partner who also has a v similar arrangement, meaning our child-free time we can potentially be together, either at mine or his. This means I kind of know what it feels like for my kids to spend so much time in two 'homes'. We have no intention to blend and will continue as is until the kids all leave home.
I was v keen to split it 50/50 as I think anything less implies one is the superior parent with a inferior back-up parent. I wouldn't like to be put in the back-up role so couldn't see how I could expect my ex to either.
I do agree with some PPs that there is abuse of the system where lazy parents insist on 50/50 to avoid CMP.
There is no perfect answer sadly when parents separate. I think maintaining strong relationships with both parents is key (where safety and practicality allow). So is accountability and expectation - I show up for my kids when they are with me and I know their Dad does too. Kids adapt and although I know they would prefer to stay in one place, they would miss the absent parent more.
Any lastly, on the impact on school/behaviour - my kids were and would be just as chaotic/mouthy if they lived in one house. And my partner's kids are polite, organised, high achievers who still are even though they have two bedrooms.