Do romantic relationships always equal burnout?

Hello all

For the last year and a half I’ve been dating a wonderful person, and after my however many terrible short-lived prior relationships I feel extremely lucky. At the start of our relationship we saw each other a few times a week, and every two months I got so ill I had to take several days off work and just sleep. It was like clockwork. We agreed to reduce our contact time to once a week, usually an overnight on a weekend, which has helped a lot. But I’m still exhausted. 

My partner has a very different sleeping schedule to me. When we’re together it inevitably ends up on me missing out on sleep, spending the week recovering, and then missing out on sleep again. We’ve spoken about it and when we’re together we try to make sure we go bed ‘early’, but it’s normally around midnight/11pm. (Which I appreciate is most people’s acceptable bedtime, but my ideal bedtime is around 8:30/9pm then sleep for ten hours.)

They were away for a month and I felt so well-rested and energised and wonderful, and while I missed them, ’missing them’ was manageable. The exhaustion came back almost immediately after we first saw each other again. I love them but I don’t know what to do, or how much I can reasonably expect from them. I don’t want them to feel isolated or unappreciated, and they’ve already modified so much of their habits/behaviour to accommodate me. (Including agreeing that if/when we live together having separate bedrooms is very much the best idea). 

Does anyone have any advice? I don’t know at what point asking them to accommodate will become unreasonable, and after decades of crappy relationships I don’t want to give this up.