The problem is a bit circular. Mozilla is flippant with money because they get it from Google and they act like it will be eternal. Assuming an absolute worst case scenario: just based on 2024 finances, Mozilla has enough money to keep running for about three years with no funding if expenses remain stable (123/41=3).

It's worth noting that Servo and competing engine Ladybird are still in development, and they do not get Mozilla money...