I think about this alot lately, but if you surround yourself with people who are also obsessed with success, you'll see people who traverse through these tests in insane short periods.
ok, the old, lot of FCAS around me, completed the journey in 5-6 yrs, a few 7-8 yrs, only know one case finished in about 13 years.
all start from exam 1, and most of them complete pre (exam1-4) in first 2 years.