We fought for nearly 3 years with a pony who had a large crack in his foot. Niether my farrier nor I wanted to resort to shoes (mainly because shoes are expensive and the pony was fully retired and sound). My farrier tried everything but the crack just wouldnt grow out. It didnt get any worse but it didnt geet any better.
Gave up in the end and shoved a pair of shoes on him. Hey presto problem fixed in 6 months, shoes came back off and never had a problem since