Feature Request - Additional purge cache option for previous projects only

Working on a project and running out of cache?
Spent the last few days working on your current project and buidling it's cahced data?

Deadlines looming?

I think it would be handy to have a seperate option to purge the cache for previous projects only, retaining cached data for the current open project to save having to wait additional time to re-render what's already been rendered.