You can flash as often or little as you want (at least whilst that image version is still supported).
Some people like flashing with latest images all the time, some every now and then and some only when there is a problem or image version is no longer supported.
Consider yourself lucky as some image teams release daily updates.
The updates are due to either fixes/improvements or new features. Some maybe only minor and may not be noticed at all.
Basically, if you are having no problems and you don't want to update then you can stay on image version you're using.