Here's Elon Musk expressing his confidence in a fully and rapidly reusable rocket just after seeing the two boosters of Falcon Heavy land for the first time in 2018.

“I didn't really think this would work. Because when I see the rocket lift off, I see a thousand things that could not work, and it's amazing when they do. 

Seeing the two boosters land synchronized, really just like the simulation, it makes me think, there really could be quite a scalable approach. 

You could imagine large numbers of those just coming in, landing, taking off, landing, doing many flights per day. 

So, it gives me a lot of faith for our next architecture, the interplanetary spaceship. We have different names for it, but BFR is the code name, and it gives me confidence that BFR is really quite workable. 

I was actually looking at the side boosters and like, they're pretty big, you know, 16 stories tall, 60 foot leg span. But really we need to be way bigger than that. 

I have tremendous confidence, obviously, in the SpaceX team. So I think we can really do this a lot and keep advancing the technology to achieve full and rapid reusability, which would have a profound effect on the future.”

Falcon Heavy launch press conference, February 6, 2018