Long post to try and avoid drip feeding. Beyond outting but I can't find it in myself to care.
Split from STBXH late 2016 at the time I worked weekends (currently 4 weeky rotation of 2.5 x 12 hours shifts) and he looked after DS (now) 2&5 - he works Mon to Fri (half day Fri). The agreement was that this would continue after split 1) so I could still work to support DS's and 2) so STBXH had contact. It has been rocky - arguments, fights and everything in between. Recent argument sent my mum to hospital due to high blood pressure (she was involved as he wouldn't leave me and DS 5 alone) I feel like this has triggered the change in situation.
Solicitors on both sides to make everything formal and done by the book regarding divorce and child arrangements.
STBXH has now hit us with, he would the the boys EOW instead of weekly as he "needs a life" - his words. I feel like I've been very flexible and offered to have any dates covered at the weekends if he needed as long as he gave as much notice as he could ie not the same day! Which has happened.
His reasons are;
I need weekends with them - I work every weekend and have done since they were babies. It's the only time I can work with childcare. Don't get me wrong I would love every second with them but I do need to support them. I also do everything during the week (school, swimming lessons, taekwon do classes and soft play sessions) to spend as much time as I can while earning enough to live.
He needs to take over time at work - I can count on my hand the amount of overtime he has done since we got together, it has never been compulsory. He hardly gets asked and he is technically only missing out on 5 hours on Saturdays as he picks DS's up from nursery ~5pm Fridays. So overtime could be done Mon to Fri if he is that desperate.
I'm basically struggling to see why you would lower the amount of contact with your children. He has them for only 45 hours weekly at the moment and about 24 of that they are asleep! 
Sorry for the long post - I needed the rant. So MN AIBU?