I started monitoring temps but to my surprise it was running cooler
I'm glad to hear that. It sounds like with the steepness of your particular hills, combined with your particular bike + body weight...you have found a balance of components that work. You might consider adding Ferro-Fluid, which would provide a safety margin in heat-shedding (plus hub-sink fins?). Another option is to did-assemble the motor (maybe next winter?) and coat the stator with water-proof motor epoxy/enamel, then cut ventilation holes in the sideplates. I mention the FF first because...once you cut the sideplate holes, it would be a pain to seal them up and go back to the previous state.
(A coffee-cups' worth of ATF works well, but unlike FF, ATF will always finds a way to leak out)
That's also why I mention swapping-in a smaller diameter rim first. It may seem to be a pain and time-consuming, but once I committed to a rim-swap, it didn't really take that long, maybe $150 for rim and spokes?. It was certainly easier and faster (and less expensive) than getting a higher-voltage battery pack ($700-ish?), and possibly requiring a new controller (18-FET, $150-ish?).
For the street (with no potholes) there are many benefits to a smaller rim, and you can always raise the voltage later if the rim-swap doesn't quite work out as well as you hoped...
If my house burned down, I'd take the insurance check, and...to replace my stretch cruiser, I'd get a longtail cargobike with a 20-inch rear wheel (ODK-II, Edgerunner, etc...), and load a 16-inch moped rim (same diameter as 20-inch bicycle rim) onto a 35mm Edge (hidden behind cargobags). Where I live, the hills are short and mild, so...I'd only need 48V. A mid drive or high volts would be a waste in my location. However, If I moved to a hilly area? I'd go to 52V, 60V, or 72V as needed.
If I moved to ultra-hills like San Francisco, I'd use a mid-mount motor, like a single-speed Lightning Rods big block. Mid drives (through the gears) seem to work best at 2500W and below, and I'd have to stock up on having a spare chain with new sprockets (replace as a set when worn)...