but how many mums do actually put themselves first?
Parents, regardless of gender, should put their kids first. It's not to say parents never get any time or resources to themselves, but they should always consider first whether the kids will be all right. In your case, your children already miss their father and he's woefully inadequate in his capacity to care for them. So no, buggering off whenever he fancies when he's already missing too much of their childhood and taking no active participation in their education and raising is not in their best interests. And it isn't about mothering.
Regardless of DH and our circumstances, 4 kids is 4 kids!
Tell your husband, I'm not sure he realises this. And four kids is precisely why he needs to be stepping up. More to the point, because they're HIS four kids. Yes, there are lone parents with lots of children but YOU ARE NOT A LONE PARENT, or at least you're not supposed to be.
I'm not making excuses for DH or doing a sob story here either, but when he was young he would regularly go for 6 months without seeing his parents as they were overseas
Well then you'd think he'd want better for his own kids, no? That they should get the precious family time with both parents that he never got? I'm not being facetious, but I honestly don't understand the defence you're trying to make here. He obviously does think kids need time with a parent because he's such an arsehole about you working. But the responsibility isn't his?
Will he step up when he takes early retirement? If neither of you are working, he'll be able to do his half of the school runs, childcare, looking after them when they're ill, cooking, cleaning, all that, yes? Yes? When neither of you are in paid employment, he won't expect you to keep on doing all the shitwork while he travels and explores and fulfils himself, will he? Will he?
I've said it before but it bears repeating...I am sick of him. I have never met him and I can feel the weight of his wants, his desires, his needs, his life, his thoughts, his mother, everything all about him, coming off your posts. His life is half over, he wants to do this, he thinks that. And nothing about your life also ticking away, your desires, your wants, which must still be dormant somewhere or you wouldn't have this thread.
Certainly nothing about your children's wants, which seem pretty simple and reasonable to me...more time with their father, more time to be reassured that they matter, that they exist independently of his will, that they're people in their own rights and not just parts of the portfolio of his identity.