always on your mind that the next satellite pass might be so low on the horizon that your unit wouldn't pick it up. When that happened a couple of times you might be 8 to 10 hours between fixes. You could get into a lot of trouble in 8 to 10 hours. I tried to keep on top of it by advancing my LOP using a DR position. I would mark the DR position prior to fixing my position with Sat. fix and then compare the two. It was fun seeing how close the two were. I got pretty good at it over time. Now we always are spot on. What a difference a few years makes.