The concept of cross-field mechanics is not only accepted, but encouraged, at all levels of football. As these things typically do, this migrated out from the NFL to the NCAA to high school. Properly, and judiciously used, it can make our jobs quite easier, and make us more effective. But, as with most things, there are times it should be used, and times it should not be used. It should not become a crutch, or a way of 'easing' up on our individual efforts. Cross-field officiating should be used only when the off-side official has a good look at the action, and can offer a reasonably good spot, if not 100% accurate. Action at the line-to-gain is not, typically, a good use of cross-field. In those cases, the near-side official simply must do what he must to get a good look at the spot, and make a judgment on the OB spot. In what should be a rare case of the near-side official getting tripped up or otherwise greatly impeded from getting a good look at the action, there is little choice but to check with the off-side guy. It is either that or guess - and we don't like guessing.
In those cases that do not involve the line-to-gain, and the near-side guy gets pushed away from the action and doesn't get a good look, the off-sided guy should be able to offer a spot. Of course, all officials should prioritize player-on-player action, and that may prevent the off-side guy from getting a look. But, the vast majority of times, the off-side wing should be able to get a look at the action going OB on the opposite side of the field, and be there to offer a spot, if needed.
I will never forget this. In my earlier FBS days, when I was an F, Team A punted, and the B receiver caught the ball, and advanced several yards, running OB on the opposite sideline. Just as the S was beginning to mark the spot, opponents that had followed the BC out of bounds started getting "chummy" with the BC, and the S - quite properly - left his spot quickly to separate the players, and prevent any UNR or UNS. When he completed those efforts - successfully - he turned back toward the field of play (now some 5-yards "north" of where the BC crossed the sideline). The look on his face was just short of 'horror' when he realized he didn't know the OB spot (no, he hadn't taken the moment to drop a spot marker). His eyes turned to me, across the field, where I, very comfortingly, was calmly holding and tapping my leg at the yard line where I believe the ball crossed the sideline. The look of relief on his face was what I will never forget. In that moment, we both fully realized the value of cross-field officiating.
Cross-field officiating. Use it. Don't abuse it.