When I got this role, I instated a culture of never closing old bugs, despite some of my managers wanting me to do that many times, and one of them even going on a rampage once and closing some of them (which I reversed as soon as he left). Some of the bugs are still encountered by new users, unfortunately, but are not fixed yet since they are not critical enough or have enough impact compared to other bugs.
To his credit, that manager also came up with a more-or-less effective formula to rate the bugs according to their importance based on several criteria. Which helps a lot with the upkeep and with planning ahead. And occasionally, one of the very old bugs will be critical enough for a large enough group of users that it will rise up in the ratings to be fixed.
I also set aside time for bug grooming once in a while, closing bugs which were fixed or are no longer relevant. Unfortunately. at this point we are a small team with only 2 experienced devs (the rest are very good but are relatively new graduates and/or without a lot of experience and require supervision) and close to 5000 open bugs and requests, and a steady stream of new feature requests and bug reports. We also have too many internal users for our own good.
It's tough. But the dude abides.
