I can't answer your question directly, as I haven't experienced Firefox problems in a few years. In the past, I experienced regular hangs and crashes.

There are a few point to unpacck here:

  - Qualifying a statement with "Full stop" is a thought-terminating cliche.
  - Due to the different hardware, operating systems, and use cases people have, peoples' experience, and the problems they encounter vary between users of PC software.
  - Milliseconds as overhead to startup may be irrelevant. Ms in most computing contexts is a timescale to be concerned with, as it's relevant for latency, cumulative operations, and responsiveness.