Serious is relative
I have to compete with 'serious' players that have no life outside of tennis (it seems), in my leagues. That's why I relish whenever I perform well. Competing against players that play in my singles league, a singles league at another nearby club, hit for an hour and a half once a week on a contract court -- and hit with the pro for an hour once a week -- these Type A's inhabit my club. They also tend to 'look' like tennis players -- it's like Wimbledon out there sometimes!
I've moved up three times now, compiling 7-5, 12-2, 9-6, and 10-6 records and am now in a league that has 4.0 - 4.5 players, over 25 of them in all -- since coming back to tennis 2+ years ago.
Myself -- I play softball, baseball, tennis, occasionally basketball (winding down on my gym time in this sport to protect my body) -- and have three kids, two that just finished playing high school tennis that I seemed to be hitting with one or the other (or both) every day that it wasn't raining. I've coached two sports, one a travel team, straight through the last six years, for my kids. During the summer I get to hit a lot, with friends. We always play matches -- but that is also predicated on my activities with the kids, i.e., openings in my schedule. During the winter it comes down to 1-2 times a month with a buddy on his indoor court, and a once a week league. I always play to improve and win, but don't pusher it to aim at the former over the latter. I read tennis books and talk tennis with a couple of buddies, also in leagues, as well as my kids. Watch tennis on TV.
That's about as 'serious' as I'm going to get for something that ain't billable hours.