To be honest unless you are placing them in your own bee yards or yards near other's peoples bees the chances of catching a swarm is pretty slim in this part of the country. If we were in the south or mid-west along the migration routes than it would be worth while, but not up here.
I have only ever had swarm traps catch my own swarms.
Get those traps out before your bees swarm
. I always thought that was the idea.
I keep putting out traps every year but have only been successful with an empty hive of 2 medium supers full of drawn/empty brood comb. Ever since then I always have an empty hive but have yet to have the same experience. I think I'm just getting better at prohibiting swarms.
Swarms that are cast from my own yard do seem to prefer an apple tree about 20' in front of the beeyard. I've caught several swarms over the years from that lone tree. Always an easy catch.