Well....If you don't have a license yet and are limited on experience I still say learn why you are spraying, and what you are spraying and when they are most vulnerable in accordance with your states recommended rules and practices.
If the spiders are year round then a broad spectrum and timed year round program should be used....but again.....it's insect and area specific based on temperature, life cycles etc.
How does one spray every 2 months sound? One spray every ten weeks?
I have thirty years experience. Just not in Spokane Washington.