How hard is it to last in IB?

Let's define someone who's "made it" in IB as having $10M-$20M (aka a good amount to live off of).

For someone who's already made it into IB and who 1) has stamina to last IB hour weeks for 40 years 2)is semi-personable 3)semi-intelligent and 4) has no prior connections, what are the chances this person lasts in IB (or PE,VC, etc)? Wondering because the major cause of leaving IB seems to be burnout.