How important is deleting old, non performing content pieces?
We have a blog with about 500 posts, many are over 3 years old and aren't ranking for much and receive very little traffic, if any. We had an SEO agency that said we should at some point clean up the old posts as we only get a certain amount of "Google juice" per site and right now it's being split across all those old posts as well as the new better optimised posts. So hurting out ability to get ranked for the new/better stuff.
TLDR; at what point should we start deleting/archiving old posts? Is better to remove them or to try and better optimise them?