Mr.Sandstorm
Casualy coming your way, stand by.
I agree that an incentive to revisit systems would be nice, to see how they grow while we're gone and interact with those people and cultures more. I think the most obvious incentive to revisit planets and systems is building relations with local civilizations, getting in better standing with them so that they'll be willing to share knowledge with us and help us out when we need it. And yes, very few ships have access to a warp drive and so we have that advantage and hence a reason why people may want to work with us, as long as we had the available energy.
Well, for this case we'd still have to stick around a certain cluster of stars for a good while, and at that point it's possible that one of the local stars will request us to aid them in making a coalition of systems by acting as an envoy of people and goods.
Setting a relay of stations to propel photon sails continuosly would be possible with anything that can exit a star's orbit, but a 0.95 c warp drive would speed the construction a lot. And once you have that relay set up, ships could probably reach speeds similar to the warp drive itself, since laser sails are independent of fuel requirements, only the max energy budget of a system.
Another bonus of interstellar relays is that you can also use it to clear a hole trough the interstellar medium to make debree and hull deterioration a nonexistant problem. Hell, you might as well go a step ahead and turn that hole into a river of usefull elements like oxigen and hidrogen flowing from one system to another, that ships can sail with and also scoop up in case they run out of basic supplies.
This would only be immediately feasible for a close cluster of stars, so the total travel time shouldnt last more than a century or two. And after that, we'll have not just a few stars, but a whole interstellar federation backing us up!