As the partner to a NRP I am the one who keeps an eye on all our money, he isn't very good with money, but I am.
His maintenance payments are his own though, I only deal with our joint incomings and outgoings. But, I am the one who knows how much he gets paid, he doesn't have a clue. I am the one who knows how things like CSA/benefits/tax credits etc work, he doesn't.
So, it was me who suggested he increase the maintenance two years ago when he got a new higher paid job. He didn't have to as they have a court order. Plus we have dss more than the original order took into account.
We are now going to have dss another night per week. So, the court order was EOW plus one week night. That morphed into two week nights and will now be three week nights. So, three nights every week plus another three every other week. So, nine nights every fortnight. 9/14. More than 50%. Oh and nearly all of all the school holidays (we did all of Easter, both half terms and all but two days of the summer - with dss going to camp for one of the weeks which dp paid for. We did all of last Christmas bar from about 2pm Xmas Eve to 9am BD and this years we're going away from 19th to 27th with him, so not sure what days she will have. We have also done his birthday parties for the last three years).
But I have not suggested he reduce his maintenance.
dp pays for all school trips and after school activities and buys clothes he needs for being at our house, so there are two sets of clothes. We have also bought him two bikes over the last few years as ex won't allow him to bring his bike from her house to ours, so he has to have one here to go to school on (which also causes ridiculous logistical issues when he goes from hers to school and then from school to ours). We have taken him on holiday at least once every year, often more (this year Norway skiing and Devon for summer, plus Scotland at Christmas and two weekend trips in between). She has taken him once for a weekend camping that her dp got free from his work. She however has had at least three foreign holidays without her ds over the past few years.
Ex is asking for more. She hasn't asked directly yet, she has said she will soon be asking for more. Over 10% more. Dp wants to resist this as there is a cost to us having dss so much now. And he's 14 so we can no longer get away with feeding him gruel 
He also often asks how much I earn but I don't care about telling him, I think discussing finance with kids is important. I think he needs to understand who has what money. I don't care if he tells his dm, my income is nothing to do with her.
I also take chunks of time out of work, as I contract, and he is always asking me when I am going to be working again - but I always get the impression this is more to do with whether I will be at home to 'look after' him as I did all of last summer.
My lifestyle is affected by this, there is no doubt about it. I cannot take two weeks and go trekking round India with dp because he can't take any more time off work due to having dss all the time. We do have holidays on our own as well, but not as long nor as interesting as I would like and would have (and did have) without him. My time and money is spent going on holiday with dp and dss. And my dp doesn't have as much disposable income as he would for us to do nice things. So I feel I DO have the right to a say in how much maintenance is paid - while accepting that dp has a right to ignore me.