If your compression is good and the bike is still losing oil there is one other possibility, but its rare.
The oil pump sends oil up to the bearings on the cam shaft on top of the heads. That is where the oil breather tube is on the rear cylinder. If the passage ways in the head are clogged up with carbon or gunk and the oil cannot flow back down to the crankcase, it will puddle up there and get blown out the oil breather tube, and sucked into the carbs from the air box connection.
There is only a very small flow of oil going up there, so when you first start the bike up it would take a while for the puddle to form in the head area, and start blowing the oil out the breather hose.
When we were addressing the problem in the other thread, where the oil was seen coming out the breather hose, I google this and found a few motorcycles that had that problem.
Im not sure how that much gunk could build up inside an engine, like I said its pretty rare, but it does happen. The bike owners had to tear their engines apart to clean the gunk out.