Bf and I are hoping to start living together later this year. At the moment we spend about 4 nights a week together, but never normally more than 2-3 nights in a row. We're together every other weekend, and a couple of times in the week (but obviously at work in the day).
I'm an only child and spent a lot of time alone (very happily) as a child. I lived on my own for a couple of years before I had my DC, and now it's been just me and them for 7 years. My DC are teens now so pretty independent and when they're at home spend a lot of time in their rooms, so I get plenty of time to myself. Even when they were younger, I used to go and sit on my own or hide when necessary telling them 'mummy needed some quiet time'
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I did live with my Ex for a number of years, however that was a pretty awful relationship most of the time and we used to generally avoid each other at home where possible...
So in this relationship, I love spending time with BF, I miss him all the time he's not here. BUT I love my own space, time for myself. He was here over Xmas, and it was lovely. But when he went home after 5 days I felt pleased to be on my own (even though at the same time I missed him not being there!). I appreciate that sounds a bit crazy 
We get on really well. It's very easy and comfortable. But I think if we're together in the same house all the time it's going to result in conflict (as after Xmas I could feel myself getting niggly at him, and I think he felt similarly - that we actually needed some time apart).
So what's the way forward? How do you manage living with someone and keeping your own space? He (jokingly) said maybe one of us needs a job where we work late/nights a couple of times a week (or a hobby which keeps us out similarly) so we both get time to ourselves. It's either that or I build a shed for one of us in the garden to retreat to...