If these are plans he's had for many years for his retirement, I can kind of see why he'd like to still do it (*)
If they are plans he's made while he's been with you, it's not so understandable. As a couple, you might retire at different times, but you still don't plan separate lives.
*However, the fact he hasn't changed or tweaked those plans, bearing in mind he's in a committed relationship, shows he isn't at all bothered about being away from you for months at a time.
Your posts paint a picture of a man who is entitled, selfish, thinks you should be grateful to live in his house, thinks he should so whatever he wants, but if you state a need or opinion you're being 'needy' (by that he means he should always get his own way and you should always give way to him. Anything else is you being needy and selfish).
Your children don't like him.
He talks about bringing in a lodger, with no thought for how that might leave you. He's committing you to living with a stranger while he's off on extended holidays.
He assumes you will be housekeeper and pet sitter while he's off having the time of his life with other people.
I think you are a useful person for him to have around but that he doesn't 'see' you. He doesn't consider you his partner, his equal. He doesn't want to spend as much time with you as he can. He treats you a bit like staff.
Honestly, I think this has run its course, and I would suggest leaving now.
At the very least, I suggest moving out and back in to your own place, and start to get some distance between you. You have very good reason - you don't want to be forced to live with a stranger in a few months time. You'd rather be in your own place with your own privacy. He can sort out his own housekeeper and pet sitter. You have a life and a paid job already.
But seriously, I'd leave him. You deserve better than this selfish, self-centred, arrogant entitled man.