I must say it is lovely to read an unusual MN thread emphasising the importance of friends. Usually posters say friendships are drama, too much work or their husbands are their best friends.
I actually doubt that is really the prevailing view, but I think maybe it just seems that way because people only tend to post on here about friendships when the friendship involves a problem or dilemma or a massive argument or something, so people naturally reply with stuff like 'This is why I can't be bothered with friendships...' or 'Who needs that drama in their lives?'
I don't think there's anything wrong with preferring the company of a partner or family to that of friends, and I would certainly say that my DP is my 'best' friend - I don't think I'd want to be with a partner who wasn't. I do have friends as well, though, and I have a lot of (drama-free!) fun when I see them. I'm not super intense about friendships and I don't see my friends a lot (just because of geography really - it takes a lot of arranging and planning) but I definitely value them a lot and we WhatsApp all the time.
To answer the OP's question - I see my closest mates about every three months, but that's usually for a full weekend with an overnight stay so we cram a lot in. I might grab a drink or some food with work friends every couple of weeks perhaps?
Hobbies-wise, it's mostly pretty low-key stuff that doesn't involve other people and often doesn't require me to leave the house, things like crafts, baking, reading, garden stuff? I do yoga most days but at home, not at a class. I go running a couple of times each week.