Where I used to live we had cockroaches and it got to a point where our kitchen was never safe. We moved right after our contract was up mainly because of this into a really nice conclave of garden homes. At first there were still some pesky roaches aloof. We noticed however that they weren't alone because there were spiders too. We stomped, vetted furniture, and finally after a while came to a startling realization. Where we failed at vetting everything from cockroaches, The Spiders succeeded and ate them, then reduced their numbers naturally. I now love spiders. Spotted one yesterday and put it on a fern I had watered recently. Hopefully he got a sip.
(and they aren't retarded, no they don't go in your mouth when you sleep)
I have always hated flies with a passion.
As a child I recognized that spiders were my best ally in the war on flies. So I have always welcomed them in my home. They only stay if there is food, and the leave once the food source is used up.
My cats usually snack on any that set up somewhere they can reach, but the rest are allowed to stay.
I don't often get any though. I'm on the 5th floor, in a city.