I did search the recurring task product feedback and did not find one to match my request. I hope I didn't duplicate it.
We have a number of tasks that only happen every other year or every 3 or more years.
Currently you can set tasks to a yearly frequency.
Business license renewals, engineer license renewals (as an example) only occur every 2 years.
We would love to see the ability to set a recurrence for every 2 years, 3 years, etc.