I often see my peers increasing their fee to me by a very small amount (5 ppm or less). To me this makes very little sense because you risk losing traffic due to FEE_INSUFFICIENT errors (until the update is propagated through the network) for only a very small gain in profit. That's why I use a lower limit on my fee increases. A reasonable amount I personally use is to take the square root of the current fee and use that as a minimum. For (very) low fee rate channels you can override this minimum to something like 10 and for higher fee rate channels maybe something round 25. It becomes even more important if you want to serve transaction from lightning users who are not online all the time and can have a very outdated view of the network. So if you want to maximize your chances of getting routes through your node (which you should) then you've got to be considerate about how you do fee updates.