The thing I read - for electric hot water tanks - was that the sediment covered the bottom element, making it harder for the tank to heat up water, hence working the element overtime and eventually burning it out. I’m not sure how that applies to gas heated tanks. Plus, I imagine sediment depends if your town gets its water from the Mississippi or from pure mountain springs.
After 14 years if you flush it you have an increased chance of something going wrong, like the valve not totally reseating and dripping, or worse they pipe coming out of the water heater instead of the valve turning. If you want to flush it go slowly can carefully and be prepared to abort if things are not going smoothly. Also buy a hose end cap (or you can usually use a hose nozzle in a pinch) to cap off the valve if it doesn’t reseat.
If you do this and not much sediment comes out you should never need to do this again unless your water conditions change.