How often do you recommend a site undergo assistive technology testing?

Assistive technology testing should be treated as an extension of your ongoing usability testing. It's not a one-time task, it should be part of your regular process to ensure that users with disabilities are included in the experience you're designing.

Every update to your site, especially content changes, can introduce new accessibility barriers. That's why it's important to combine automated checks, manual audits, and assistive tech testing on a continual basis.

Also, remember your users are testing your site in real time. Make sure they have a way to report issues, and consider compensating those who participate in formal testing. The more you can involve real users, the more usable and inclusive your product will be.