I am also at level 37, have a bunch of frames and wheels in my garage, more than i can keep track of, and of course the Tron. Right now I have 6.5 million drops and there really isn't anything I want to buy except the ZIPP disk wheels but that is at level 45. Still I'm using Zwift to maintain and hopefully increase my riding performance for this upcoming season. I'm planning on going hard and heavy on Zwift until April 15. I'm also planning on importing a Training Peaks workout program into Zwift in a few weeks to see how that goes. Last summer I hardly used Zwift at all, this summer I think I will use it more, training during days the weather isn't nice or if time constraints keep me from riding IRL.
For all of it's warts, Zwift has for me been a big help in getting my fitness level up from where it was two years ago, a pathetic individual I was. When I made the commitment to get the Tron and all of the route badges, it forced me to ride more and harder than I would have ever done on my own, and certainly way more if all I had as a stationary bike with no interactive stimulus. For that reason I'm a fan of Zwift although it could be better it's still a great value for the cost.