I never set a den or lodge entrance,but I will put my castor mounds close at times. I gang set so that I get them fast, before they figure out what is going on.Once set 8 330s in less than 100 feet--about 50 feet from the lodge,6 castor mound,1 crossover and 1 little channel.All 8 sets had beaver in them the next morning.
I have very few creeks that I trap--mostly lakes and ponds.But like charles said, you do not have to set near dens.
In the fall I set on sign,fresh chews,fresh cuttimgs or frsj pullouts,I don't even bother looking for lodges or dams--if I have sign I set it.
In the spring,I don't worry about fresh sign.I make my castor mounds and let them come to me.There is so much beaver movement in the spring,that I don't have to worry about fresh sign.
A castor mound ,is like the field of dreams--- IF YOU BUILD IT---THEY WILL COME.
Tom