Very minimal on a healthy F4R
That black car did 20K miles on that rebuilt engine and there was never any actual liquid really collected during that time, just a tiny bit of discoloration from the slightest amount of vapour.
My old turbo where I was seeing how far I could push the standard old engine (already had the bits for the replacement so just being curious) and was completely ruined on bore seal etc, I was getting 2 litres of oil out of the breather in a single track session!
I made a Cosworth Group A style setup though that seperated the oil and air and put the oil back into the tank.
Funny thing is, even in that state it STILL went like hell!