I made some last year and it was fantastic if I do say so myself. I let the peels sit in the vodka for 2-3 weeks but there was still some color in them so I let it sit a week longer before adding the sugar syrup. In this year's batch I will add less sugar since we did find it overly sweet, but maybe that is how it's meant to be...
After I added the syrup, I left it another month or so with peels in but swirled the container once a week. We sampled it at 2-3 weeks after the syrup addition, but left it stewing and it definitely improves with age.
I think 4 weeks is the minimum, but I'd start it sooner if possible to give it time to mellow.