from the voice of very recent experience...speedplay says to replace the cleats after 5000 miles, and unless you have always walked on carpets and grass with 'em, I'd say buy new ones. The springs wear, and then break at the least fortunate time. the bottom plate wears, until the edges could be used in a prison fight. Trash 'em and buy new.

Oh, and the two floating nuts in the middle of the shoe are for SPD cleats, and you can squeeze a little locktite or shoe goo in 'em to keep them from rattling.