All valuation is garbage in garbage out. A great way to sanity check your assumptions is to see what the market is thinking re: growth and returns on capital via a reverse DCF. The key assumptions to flex here are competitive advantage period and growth. 
The stronger your moat, the longer your CAP, and the more shareholder value you can generate. All companies are cost of capital businesses at terminus, but the longer you can delay that, the better. I did the above quick and dirty analysis to sanity check where $MSFT is trading
I don't scrub historicals, I haven't checked consensus estimates, but at the very least I get in the ballpark of what the market is currently thinking and whether I have strong enough conviction in a differentiated view to continue digging. Highly sensitive to inputs
Now I can say, what are the odds that $MSFT hits a 12% CAGR over a 20YR CAP to justify today's valuation? Are the odds in my favor for a winning bet? @borrowed_ideas had a great post summarizing this approach.
