> I think issues left open > 12 months is antithetical to the idea of lean/agile and could be a sign of suboptimal project management.
Totally depends on the nature of the project, its policies and users.
Any popular FOSS project that allows anyone to post a bug, and doesn't just close unattended bug reports (which is bad imho), is likely to end up with some (usually minor) bugs open over 12 or more months.
OSS doesn't care about lean/agile, those are ideologies consultants sell to enterprises.
Things are done when they are done.