Thank you, I love that you have pointed out the difference between heuristic analysis and cognitive walkthrough. As people often refer to cognitive walkthrough as heuristic analysis when it isn’t. However as I understand it heuristic analysis is a technique for the non-expert so you need no experts for it rather than 3. What you need is 3 people.
If you give an interface to an expert to look at, they tend to naturally do a cognitive walkthrough whether they know what it is or not. I believe there is little benefit in having experts do heuristic analysis. It’s like ‘teaching your granny how to suck eggs’. There is a tendency to map the findings from a cognitive walkthrough back to heuristics which is largely pointless in my opinion.