I think it depends both on the piece and on how often it's posted. More delay, more call for a recap. I think the more...informal of a piece, the more you might have call for a recap too.

Taking Herbert West as a model, not only was it appearing monthly, HPL did not consider it to be serious at all but tongue-in-cheek. One might even call it camp, a la the 1960s Batman TV show. On that series, the recaps are part of the fun.

So I think no recaps are fine in most instances, but if you use them, consider their effect.