Well, as for me, I am a musician, was very involved in a band and now very involved in recording my own stuff, and am also very involved in my mini painting hobby and i am definitely a grown-up geek...
BUT I am also married and a step dad of triplets teenage girls and am working a full time job....so you'd think that between my job, my family and my artistic hobbies, I am living a life of conflictual relationship, but not at all!
When I met my wife, and started to get serious with her, I've been honest right away, and told her how much my hobbies were important for me...a few years later, I am living with her and her kids, moved from the other side of the planet to be with them, and they completely respect my artistic occupations...
so yes, I spend a lost of time recording or painting, but i also teach guitar and painting to my kids and my wife LOVES my minis and my music, and respects the time I need for that just as much as I respect the time she needs for her own past time, which don't keep us apart at all, and leave me some time to spend with the kids too...it's just a matter of reorganizing your schedule..
I'd say it evens gets our relationship stronger because we have our own space while sharing things together, and to me this is the perfect alchemy...
So, bottom line for me, be honest right away if you're getting involve with somebody and tell that person about your hobby(ies)...he/she doesn't like it? Then this is not the one to get involve with...and when there is kids, there is always time to squeeze in some hobby time, and when they grow older, you can get them into it too...