Having enough lift capacity to take a shot at putting a pair of telescopes out far enough to exploit solar gravitational lensing to resolve exo-planet surfaces would be a hell of a thing. Orbital refueling would mean we could reasonably build something big enough to be able to boost out that far (would still take decades to arrive).

Isn't that 500 AU out?

Yes, but the trick with getting there is building the vehicle. Time takes care of the rest (you'd do it using ion thrusters).