Both the preliminary and the full check are done on the first flight of the day, not every flight. And as to Nick's question of why they need to be done that often, I have no idea. Obviously Bell has some concern about it, but I've never been able to turn off both systems at the same time. There are a number of systems checks in the 412 that seem rather needless to me, but they're on the checklist, so I do them. The 412 hydraulics check is little different from the S76 check, and that is done daily also. Total loss of hydraulic power is one of those things that will kill you, unlike engine failure. It's obviously not likely, but the check only takes a few seconds, so I don't worry about it.
As for Scorpiones Pungunt's original question, I don't think you will have a serious problem on the ground, as long as the controls are neutral or very close. You wouldn't be able to move them, but on the ground you don't have to. I'm not sure there would be that much difference between 80% and 100% Nr anyway, and 80% is the minimum RPM for a 412 (another consequence of the remarkably poorly designed main rotor system). In general, I think it's a good idea to do things the way the manufacturer recommends, because there is usually a good reason for doing them that way.