Sorry I can't really be of any help with pest control question/how long.
We dust our yard an around the house with a product called Sevin 5% dust, it kills over 65 different types of pest. We live in the country and have hundreds of spiders and many other creepy crawlies.
You can actually put it directly on your pets bedding an your pet even(great for fleas & ticks).
About the safest, effective, and cost effective that I've been able to find.
Maybe by my posting it will bring this thread back to the top of the pages so more will see it.

BarbaraSlave to...
Lola, Gus, Roux, Flame, Blaze, Itty Bitty, Checkers,
Ms. Tiggs, Zak-n-Wheezie, 3 cats, & 1 box turtle
Zak-n-Wheezie ~ 2-Headed Bearded Dragon(s) viewtopic.php?f=1&t=79821&start=0