Of course almost all startups expect a long live, but strategically it may be better (for the founders) to close when the fundamental assumptions are no longer valid, in order to do a future clean restart in a brand new endeavor (usually after a detox period).
Opportunity cost is very real. Chasing the wrong thing for 5 years can leave you broke instead of pocketing 7 figures gross elsewhere
Agreed. I think building a startup should also rather have a fast failure in case it doesn't work out. I've seen friends trying for several years, only walking away in the end with almost nothing.