From the experience in my company there were quite a few issues with short haul captains transitioning to long haul flying. Not the flying itself, that is easy enough and usually easier on the big bird. However, the whole long haul stuff, route experience etc. required more training than was initially expected. There were a lot complaints about the first few who did a very rudimentary training and especially a short LIFUS phase. Later on training was improved and LIFUS was extended by a lot which fixed those issues.
Not really a big thing, but the right training is required, and i would expect airlines that fly predominantly long haul should have that in place.