I set my Millenium Mapel Gretsch USA Customs up yesterday and noticed that the bass drum has developed what I think is referred to as finish checking. It actually may be called something else. The lacquer has hairline cracks in it. They are unnoticeable unless you are looking very closely. What causes this and is there anything one can do about it short of refinishing or recovering the set? It seems that Gretsch finishes are prone to this. Oh, I almost forgot to say that they are 17/18 years old.