For myself at this moment, I have logged exactly 400 games as part of my ongoing backlog. Of course, I'll play games not backlogged, the backlog will grow in size, and certain games will eventually retire from my backlog without ever having being played in the years to come. In practice, my backlog will almost certainly never be complete so long as my interest in the hobby remains. However, the question I proposed in the opening post—how long do you project for you to complete your current backlog at its current state with no new titles being added to it—is what I'm most curious about.
When thinking about that focused question, it's obviously difficult to come up with an idea since my personal backlog is so large. But were I to only play games from my backlog while maintaining the rate of play I've had these past few years, I imagine it to be around fifteen years at least. Based on numbers, that's nearly a halved rate of completion that I've been steadying, but a sizable part of my backlog includes games with lengthy completion times. Of course, I tend to play through games slowly while wanting to engage in as much of their content that I'm interested in should the effort and time to do so feels balanced, so it may take even longer.