For a more MMM type of response:
"Your liability limits should equal your net worth" is totally bullshit advice and isn't based on reality. Like everyone else here is saying, get limits to cover the most expensive thing you are likely to be liable for that you can afford because if you are sued for more than that, just assume you'll be going bankrupt.
Personally I see the most expensive thing I could do as either "I fell asleep at the wheel and crashed into a minivan full of attractive, young cheerleaders" or, "the house I rent out blows up while full of attractive, young cheerleaders." I use attractive young cheerleaders as the example because they win huge settlements in court compared to old, ugly people with no dependents. Young attractive people who are killed win settlements of between 1mm and 5mm per person in court. So worst case for me, 8 cheerleaders at $5mil each is $40million is the worst thing I could do. That's the cap for liability limits, not my net worth.
The only question is "how bad is it if you went bankrupt?" If bankruptcy is "I might commit suicide" bad, you need to insure against the worst thing you might do ($40 million). If bankruptcy means "oh well, I don't have any un-protected assets anyways" then you can get minimum coverage. If you're somewhere in between like "I guess bankruptcy makes me 3 years farther from FIRE than I thought, oh well" then maybe you cover X% of the van full of cheerleaders.
For me today, that math works out to $1 mil in umbrella coverage. As I get closer to FIRE, that number will go up because bankruptcy would be worse for me. I don't think it will ever hit $40 million for me, but it might be close to that high in the couple years leading up to my FIRE date and slowly go down as I get closer to collecting social security. To each their own.