Is there a country where most of your research is done? If so, join one or more.
I joined the Australia Project because I am Australian, and my main focus at the time was Australia - even though we have no pre-1700 records.
I have since joined other Projects, where there are pre-1700 records.
I still get the big warning when I edit a profile where the dates are pre-1700. I believe it is s standard message to remind us that we need to be more careful when working on such profiles.