I'm getting ready to split my single area OSPF network into a multi-area deployment. Right now all the links between my core devices are either /30 or /29 in the 10.5.0.0/24 address space. My concern is that after splitting the areas there will still be some of those address spaces outside of Area 0. Should I change the address space I use in Area 0, and if so, what would you recommend?
Yes. A reasonable amount of prefixes to start thinking area segmentation is perhaps around 1000, with frequent flapping and intensive SPF recalc.
Instead you have a small network, try to keep it the simple as possible.