“You should always have TAM in the back of your mind because as a product leader, your product is going to continue to evolve. Serviceable for me in the future is different than what it is today. It's always important to figure out what the delta is between your TAM and your currently serviceable addressable market.”

SAM evolves as your product evolves — keep TAM in view as the ceiling

Today's SAM is bounded by today's product. As you build, the line moves. Keep TAM in view as the ceiling you're building toward — not the number you plan against — and watch the delta close as new features make previously-non-serviceable users serviceable.