You have too much crap in there girl! Your saddle pads are like a pillow top mattress for them! Minimize the saddle pads and/or put them in a storage bag. Cover everything in plastic or keep them in plastic boxes. I live in the country with my barn 100 ft away... I should really be the spokesperson for tupperware because everything is in plastic containers. Ask the other boarders to do the same! I'm sure they find it annoying as well.
Traps work but I HATE TO TOUCH THEM! YUCKY!! Nothing like handling little wooden death sponges with mouse guts on them.