Dear Ms Whirly.
My (probably imperfect) understanding on this is that LBBB is bad news(very), RBBB shouldn't be. The issue with ECGs seems to be when they show a change. Mine was diagnosed on my first ever ECG (RAF Biggin Hill 1976) and has shown on every one since. 23 years of mil aviation and 9 of civ later I guess it's still there.
Hope this helps - good luck
DH