I am thinking about purchasing a Nikon F body with a working meter (FTN). How reliable are these metered prisms compared to earlier models? Do the cells have a certain life span that will expire at some time? Not to long ago I purchased an F2A with working metered prism. I absolutely love this camera and I was hoping to add an older F model to my collection. I try to purchase older cameras in near mint condition in order to actually use them as well. I am debating whether I would be better off just getting another F2A instead of an FTN. Any suggestions? Anyone have any comments on the FTN? (Reason I am thinking about the FTN is because it was the last production F before the F2, so I am assuming the meter and mechanical parts are hopefully in better condition than older F models).