I had my catch can in place for about 12 months, it works very well, I reckon I would catch about 50-100ml of oil every 5000kms.

I've done a shifty and cut the hose that leads back to the turbo, blanked it at the turbo and the other end just feeds out to the atmosphere. The catch can is still in place & catching as much oil as it always did. I no longer get oil mist into the intercooler and there is no sign of oil at all out of the atmosphere end of that catch can hose. I've also removed the rubber ring around the catch can lid so it doesn't seal 100% just in case pressure needs to be let out, even though those Provent CCs are meant to have a pressure relief valve in the lid.