Why bother to delete old content? It is indexed in search and if someone stumbles into it from a long tail search, why not? We always try to keep our content and we ask our network (we manage a platform of publishers that we connect with brands for sponsored content) to keep the content "evergreen" so that it can be found at anytime.
Also, people look at their social media streams at different times of the day / week. Posting something on Twitter to get a hit is much harder than Facebook or LinkedIn. You can continually repurpose on those platforms as well as a site like Medium to get the maximum mileage out of your story.
What we did is to write a guest story (which should be original), then post it on our social, and on our own blog but link to the original (so we don't get dinged by SEO by using the rel=canonical tag).