Subnetting /48 to one /64
I have simple questions about IPv6 subnetting.
We have EDI and are given /48 IPv6 addresses but need only one subnet. Currently we assign /48 addresses to all of our devices but I thought I might need to subnet it and assign /64 addresses instead because IPv6's host subnet is /64.
My questions are:
Is it OK to use entire /48 addresses instead of subnetting it to /64?
If I need to subnet to /64, do I need an additional router for it?
Using an additional router for subnetting seems a little wasteful in this case and we'd like to use only one router (/48).
Thank you so much.