Yes, some people come to be able to do many days on on a board. Im a punter and even I have done two days on a board for extensive periods. Its just a case of building up gradually. Session length is also important. How long are your sessions? 2 hours on two consecutive days is much better than 4 hours then a rest day for training strength and power (IMHO). Personally, I used to sometimes do 2 hours board on day 1, then 1.5 + 20mins max hangs on day 2. However, thrashing on a board (past your best, tired and sloppy) is not effective training and leads to injury.