How often should I re-engineer the menu?

A meaningful review every quarter is a sensible rhythm for most independents, with a closer look whenever supplier prices move or you add a section. The data only becomes reliable after a dish has sold for a while, so resist re-pricing on a week of noise. The exact cadence depends on your volume and how fast your costs move — your own sales and cost data tell you when a line has genuinely shifted.

From Menu Engineering: How to Price a Restaurant Menu for Profit — the full reading, with the method behind this answer.