I have heard that if you have some 2-week to 1 month old coffee beans (since roast date), you should grind the beans finer as time passes. This is for the pour over method. Is this necessarily true and why? And of course, there could be possible secondary factors/combinations based on equipment used and type of coffee.
The reason this is suggested is because beans essentially lose flavor over time. They go stale and their oils go rancid. Grinding finer exposes more surface area of the bean to the brew and helps you eke out a bit more flavor when the bean is old and stale.
However, doing this for pour over can backfire as pour over is highly sensitive to grind. Too fine and your pour over won't drain; the filter will clog.
Try it first with your normal grind, and if that's no good, dial it one or two clicks finer. Much past that and you're in no go territory for the brew method most likely.
Roasted coffee changes its flavour over time - you might notice changes in acidity and bitterness. If your coffee gets too bitter you can compensate that by grinding coarser and if it gets too acidic you can compensate it by grinding finer. Also, while the coffee degases its density and also the availability of soluble material inside the bean change.
Don't worry too much about the time it takes for your pour over to be finished, try to adjust by taste.