Selecting the strength of a password is completely a personal choice, so I don’t mean this to be critical, but I have to wonder if a 100 character password is actually significantly more secure than a 16 char unique password (i.e., one with numbers, letters of both cases, and symbols)?
And the NIST and even Microsoft recommend that it is no longer best practice to arbitrarily rotate unique passwords. Part of the reason is that modern hashing algorithms now make it too difficult to reverse engineer passwords, but that wasn’t always the case, hence the recommendation to rotate passwords frequently.