Staying put is sound advice if you know moose are in the area. Even if you call away for days and see nothing, stay put. At the beginning of the season the bulls group up, i don't think they do that cause they wanna be friends and hang out, but because they want to know who else is in the area and scope the competition. As the season progresses they get that testosterone going and start to separate the strong from the weak, this quickens when cows start joining the group. Its at this point the dominant bull in the group either chases off the weaker or kicks their ass and they leave. When they leave they will travel long distances to find another 'party' and see if they can be the big kahuna there. This is when you catch em, they have heard you calling and will have a mental note of where you are, once they get kicked out they will come to you to see what's going on, this process may just take a while.
Last season we watched a high 50's and a 65 incher hang out from late august in the velvet all the way until September 9th. They were up high in a spot we could not get too, but we could see them from below every day. We called at em the whole time, they could hear us as they would look in our direction, but they had their group going with a few cows and no reason to see what we were doing. Surprisingly, we watched on the 9th as they finally had enough of each other and slammed heads in one of the coolest fights I have ever seen, and that high 50's chased off the 65! He wandered off in defeat down hill, and in our direction. We raced to the same spot we had been calling from and sure enough he appeared out of the wood line heading that direction. Threw out a few light cow calls and he came right in. After he died we saw he had old scar tissue all over his nose, and his last fight put another puncture wound in it, he wanted none of that! Overall he had a bad day. Its easier to stay put when you can see bulls, but the advice is still sound. If you know moose are in the area, stay put. I have a few stories of guys calling for days, then leaving and we shot moose from their calling spot shortly after they left.