For me, running/playing in actual D&D games take up less time than participating in the hobby.
By "participating in the hobby," I mean browsing/posting websites and forums like Enworld, WOTC's boards, etc; planning trips to conventions or RPGA events; actually going to conventions or RPGA events, chatting with friends and other gamers about the hobby in general; etc.
The participating thing really doesn't take any more percentage of my time than other hobbies I have or what I see other people doing with their hobbies.
I work with a guy who is into fishing. I daresay he spends more time reading websites about fishing, reading magazines about fishing, reading reviews of new equipment, planning trips to go fishing that may or may not materialize, keeping his eyes out for good fishing spots, talking to other fishing enthusiasts than he does actually fishing.
So it's not that unusual.
In my opinion, it's like anything else in life. Trust yourself to see if you're stepping over the line or becoming addicted to a particular thing. If your hobby starts negatively affecting your family, your religious practices, your job, then probably it's time to take a step back and realign your priorities.