Thanks, really interesting responses!
I thought it was a good exercise because when I did it, the types of investments that I looked for was much different from my usual set of ideas.
There's less focus on valuation and one-time business improvements and much more emphasis on growth, business quality, competition/disruption/longevity and capital allocation.
The 15Y total returns for AXP/KO are decent when you include dividends. But LearningMachine is right, it is a very difficult question to answer, even for a master like WB.