I've had the Mishimoto can on for ~800 miles and about a month now. I decided to open it up to see the accumulation. To do this, I removed the passenger side headlight. Three bolts, took me about 3 minutes to get the headlight out including time looking for tools. T30 torx bit and a phillips head
screwdriver. THen there is plenty of room to stick your hand down there and unscrew the OCC.
The good news is that there was a small puddle at the bottom, but no serious accumulation of oil. Which is to be expected, I guess. The good news is that the catch can is catching oil, and the better news is that it is not catching that much oil, either. This means that despite the Mishimoto can being smaller than some of the other options out there, it doesn't really need to be that big.
I'm interested to see if accumulation increases as we get into the colder months of the winter.