Hi Roman,
Good question. I've dealt with this issue quite a bit. I think one element worth considering is the quality of the posts and what stood between them and organic success. I've found that pages on our site often didn't succeed for reasons that were in fact fixable. So, before declaring search success bankruptcy on them, I've tried to breathe new life into them... if the content warranted it. This could be adding content, refocusing on a different keyword, improving the link profile of the page or the on page elements. In any case, making good content isn't easy, so best to not lose some that could have worked.
Having said that, I've 301'd one helluva steaming truckload of old/failed pages and had good success, as well as a warm satisfied feeling afterwards. Best of luck!
Mike