Whatever you do make sure it's your decision, not your partners. I made the mistake of listening too much to my partner & the week after I confirmed the date I was going back we split up & I just wished I'd done what I wanted, which was to take the full 12 months off. My decision could not be revoked.

I was in the kind of position that is very difficult to learn & the person who replaced me managed fine (my coworker took on all the difficult stuff), so don't think you are letting them down by taking the full 12 months - if that's what you really want.

You can never have that first year back so think very carefully about what you want to do. It's not easy going back full time either so have a chat about the possibility of going back part time. I never in a million years thought I'd want part time but when I came back I spent weeks negotiating it & from next week I work 3 days per week.