Is it possible to have Octolapse save to external storage (like a NAS) so I don't keep writing to the MicroSD card?
You haven't said what system OctoPrint is installed on. I guess it is OctoPi.
You could mount the storage on /home/pi/.octoprint/timelapse but how this could be done depend on how the NAS exports the storage.
Yes, it is OctoPi. I can export it via iSCSI, CIFS or NFS.
I have it setup to use /nfs/timelapse, /nfs/temporary & /nfs/snapshotarchive where each one is a NFS export on the NAS. Should work fine correct?
Your setup should work fine.
One workload NFS isn't very good at is writing, especially many small files. It does work and you have to do much writing to see the limitations but try to unzip a large archive with many small files. Maybe instead of /nfs/temporary you should use an iSCSI volume for temporary files as typically short lived small files doesn't even get flushed to the disk (maybe not even the metadata) but use only the buffer cache. With NFS at the very minimum all metadata changes have to be communicated to the NAS.