I have recently purchased a 55mm 2.8 on the auction site. The lens is in wonderful condition except for the smallest bit of oil on the aperture blades. This is a known issue with this lens, but it doesn't seem too bad with my copy. The blades are not gunky, just the hint of sheen on every other blade. I have tested the exposure at all apertures, and have tested it stopped down at fast shutter speeds at 4.5 frames/sec. Exposures are accurate and consistent throughout the range. Question: Is it inevitable for the oil on the blades to get worse? Or is there a possibility that it will be fine for years? I suppose that once the lubricant separates, it can only get worse?