Can anabolic steroids permanently alter ones sperm count once discontinuing use?

Possibly!: It's not the discontinuation of the steroid(s) that suppresses sperm production - rather, it's the prolonged/repeated use that results in "-" feedback inhibition/suppression that will manifest as chronic hypogonadism and male infertility. How long is "too" long likely varies from individual to individual as well. Best not to take it if you don't really need it!