Since getting my E-M5 and 12-50mm lens last year I have made use of their weathersealed properties on a number of occasions, but have found the maximum aperture of the lens a bit limiting given that the lighting conditions are generally quite dim. I have been wondering about some alternatives which in the native mount are quite expensive, and have found a former studio selling a whole bunch of used Olympus 14-54mm f2.8-3.5 MkI lenses for only $AU129 each. I'm aware of the AF speed limitations of these lenses on my E-M5 which is still a big consideration, but my greatest doubt is how well the seals age over time given that the lenses might be up to 10 years old. My sole interest in them is as a weather-sealed zoom since I have a good weather option so if I can't rely on the seals I won't worry about it. Thanks.
So you have me wondering, how much is a set of seals? Would it cost more than the savings? That's probably your real concern.
Sorry I don't have an answer for your question about the durability of the seals, but I just wanted to say that the 14-54 Mk II might be a better option for your E-M5, since it is CDAF-enabled, and a used one in decent condition can probably be found for a little over US$300...
I love the E-M5/14-54 II combo when it's raining. Dunno about how long the seals can hold up in general but mine has taken it on like a champ.