Hah, my hobby turned into obsession after about a week.
When I first told my wife I was going to try brewing my own beer she just laughed at me and was like, "whatever, you're a lazy piece of **** and won't even mow the lawn let alone brew your own beer."
Then I started reading the classic homebrew books. She was still saying I was crazy and said I'd never read them. Then the UPS guy dropped off a few big boxes of equipment, so she started to think I was serious. Next thing she knows I got the whole house smelling like wort and hops.
Now there is some aspect of brewing going on at least 4 days a week. Whether it's soaking bottles to remove labels, creating a starter, getting a present from the UPS man, building a wort chiller, cleaning equipment or actually brewing, something is going on. The SWMBO isn't laughing any more. I might be lazy, but when it comes to good beer I can become the most motivated mofo you've ever seen.
So, weekend hobby? Sure, it starts out that way. But before you know it, it's' consumed every available free moment you have. That's not a bad thing, but it's much more than a hobby I've had a lot of hobbies over the years, but this is the ultimate.