Spear-phishing by its very definition is a highly targeted attack. I wouldn't count on any level of training to prevent someone from getting phished. Given some of the spear phishing campaigns I've seen, I wouldn't trust even myself not to fall for them.
It's a problem that needs to be solved with technical solutions like hardware U2F, locked-down customer support devices (e.g. Chrome enterprise policy managed ChromeOS devices), and special account VIP/anomaly locking and auto-escalation.