My drives currently have an older firmware version installed which is why I would like to update the firmware on them as an update is required.
I think that what frumper15 was asking is "have you hit a bug that the firmware fixes?" Just because a new firmware is out doesn't mean you have to update. Now, if there are a number of fixes that address really nasty bugs that you are likely to hit, and luckily haven't, then you might consider it. If there is a giant performance or longevity boost, you might consider it. If it is just because there is a new firmware out, don't bother unless you just like to tinker.
Assume you will brick one or both of the drives. Theoretically, you can survive loss of one as that is the point of RAID 1. Still, take an image of both disks with your favorite tool. A regular old spinning drive big enough to hold raw images of both is under $100. Personally, I would take a raw image of the disks, no intepretation, just a sector for sector copy.