being that you have a rotating shaft and a stationary stuffing box so to speak, where the seal sits in the groove which is nothing more than valve/pump packing it's going to leak to some extent. if it didnt it would burn up and completely fail. the thing is how much is it leaking. i have two 270's with new seals in them. the one in the ashton leaks slightly more than the one in my 40. they were installed by two different people which the one in the 40 is from "best gasket" and i like the way its made. i know from reading thier installation instructions using the proper tools to seat the packing in the groove and where you cut off the excess is critical for good performane. as for my leaks compared to how they leaked before engine replacement they are acceptable to me. if it took a year for the oil to go from the shaft to the drain hole then i wouldnt worry. remove the cover and wipe it clean and see how long it takes to drip back out.
