If your spider service treatments do not include ALL potential Spider harborage areas out of the rain and sun, you will not achieve complete control of Spider populations at your residence.
Good examples are: property line privacy fences, cedar hedges, undersides of low level decks, utility sheds or other structures away from the home itself.
These are excellent proven harborage areas where over looked spiders harbor and multiply if your current contractor neglects the extending perimeter areas on your property. Successful spider control measures will only be limited at best.