I've been with DP for about five years now. We've lived together for 3.5 years.
I have been given a job opportunity overseas. It would be really good professional development, but dp couldn't work there. As we are not married, he couldn't live out there either. I'd aim to work out there for about 2 years.
He could visit on a tourist visa for up to 6 months in a 12 month period. Realistically he'd probably do a month every 3-4 months.
Money wise, we could make it work that he keeps renting our current central London apartment but would need to sublet it if we came for extended months at a time. He can work remotely whenever he wants (obviously there might be problems with local rules.... but what they don't know...). It would feel too unfair to make dp move out of our shared home.
I'd probably go into a flat share which might be a bit of a shock to the system.
Has anyone done something like this? Does it work?