I think the answer for Yury is that we have not come up with any regulation requiring its check, but that it is a good idea to check it before an ETOPS sector, preferably on the ground where it can be fixed if required as well as in the last hour of cruise for the next ETOPS sector. Basic airmanship, I would suggest. Also a good idea to give it a quick check after a long leg pre-ETOPS (if you do that). I do not think it is practical to have it checked in the air on the trip before an ETOPS flight UNLESS it is written in the Ops Manual as a check EVERY flight, since I do not know of any crew that will reliably know the a/c is next departing on an ETOPS flight.