Every floor i clean i reseal...even floors i have laid a year ago that i go back to maintain i reseal. But its up to you if you feel confident applying a sealer. I'm doing one in 3 weeks 50sqm limestone kitchen floor, he had it cleaned not by me and to much sealer was applied. I have to strip the old sealer off to get the stone back to the original state then apply two coats of sealer, and its costing him a fair few quid to get it right. Give me a call if you want any advise about applying sealers etc.