When is it time to update/revise messaging? Is a regular update cadence wise, or is it product/market dependent every time?

I wouldn't say there's a regular cadence to update messaging, but you should look at it every year to see if it still aligns with the value you bring to the market/customers and your differentiators.

You should continuously test your messaging. One of my favorite ways to do this is to run ads to your ICP using your main message and value pillars.

If you prioritize listening to sales calls and interviewing customers, you will be able to identify trends and keywords and how they align with your overall messaging. If anything deviates, take note of it. If you hear it enough times, you can create an ad campaign around that message and keyword to test its accuracy.