You should monitor awhile before you RMA your drive. Just because you do a RMA doesn't mean you will get a "new" drive, mostly refurbished. Furthermore your warranty is for 3-5 years depending on the model of drive. The NAS can take a hit of bad sectors on hdd that is why Synology reserved 10% off the total drive space for this, to relocate bad sectors. If your bad sectors are not growing you are better off with your current drive. This is only my opinion after RMA'ing many drives before. I have received dud drives before after RMA too.