4AGE Life Span....Attn 20V Owners.....!!

Hello!
well nowdays as i am looking for engine to swap in my Sprinter........so i have 4AFE and 4AGE as options..4AFE is short nowdays in market and 5AFE taken its place quiet well....same looks with lil low power but still its in market.....!
so now i have 4A/AFE and 4AGE 20V BT or ST now as options.....!
well as i am discussion about swap thing with my one of friend......so he clearly said that don't get 20V 4AGE......when i asked reason he said that he use 2 4AGE 20V....one 4AGE 20v ST and one 4AGE 20V BT.......!
After swap.....till couple of months.......both of them respond so well as power is quiet good...but after some months...it start losing power and white smoke is what he notice.....! he experience same thing with 20V BT.....!

well i am quiet in doubt after listening that bcz to get that 4AGE BT thing..i have to spend around 50-55k and i don't want my money wasted in thing like that......!
i know 4AGE 20V is designed to be run on 100ron fuel but its impossible to find it or afford it.....so some ppl use it on Premium 87 RON while High Octane 92 RONS is also there.....!
4AGE 20V and earlier NON TVIS 16V varient also have Knock sensor installed as it retards timing if it senses any knocking....!
so what are you experiences with your 20V's
Hashim Bhai...Rashid bhai and other 20V owners.......put your experiences along with fuel/oil you ppl use and what you think what can be the reason behind 20V few months life span.....!
All others expert and members are welcome....!