There's a big world out there, and for some of us there's only so much time and money available to see what we can. There are very few places we've been that we wouldn't necessarily care to make an effort to return. Other places we definitely want to go back (Ireland, for starters, and Belgium, and Bulgaria, and . . . ), but haven't made it yet for another visit.
Long before we were married, we each first visited Europe back in the 1970's, and in the ensuing years, we stayed in Beynac, France twice within a 3-year period; same for Venice, Italy. I'd say those count just as much as Paris, to which we've been lucky enough to visit on several occasions :)
This past summer, we were in France, and had just part of a day and evening to visit Lyon before heading on to Nice for a week. I actually went back to Nice 2 weeks ago for another 1-week visit with a colleague from work. So even twice in 3 months isn't too much!
And we've already booked an apartment for 3 weeks in Lyon next summer. We had such a good time on our one day, and that fabulous city needs more time. Go wherever you can, whenever you can, and don't worry about repeating . . . there's always some place you're never going to get to go, no matter where else you've been.