Are the last few hours of a 36 Hour fast most important

[Kunwar]

1. Question 1 - There are times i have broken my 36 hour fast in 33 hours, and i have been told that i should have waited for 36 hours , as the last 3 hours were tyhe most important . Is that true

2. Question 2 - Is there any holy grail such as 36 hours, or is it obvious logic that 36 is better than 33 , just as 40 is better than 36 . And all fasts over 30 hours will give good benefits