Hi Sean Menke - the DOL has guidelines of best practices that should be followed by all Plan Sponsors and Employers. Benchmarking for ALL providers in a 401(k) plan should be done at least every 3 years, if the plan is under $10M in assets. Every other year if the assets are $10M - $100M. And year year if the assets over $100M.
I hope this helps! Please reach out with any other questions