I actually have 3 batteries for my two Radrovers. I had a battery fail to re-charge and Rad sent me a replacement. Did a lot web researched and got some great advice from folks on this forum and I was able to repair the in-op battery on my own. I now share the 3rd battery between the two rovers.
Sounds like you are really pushing your battery to the limits and hitting a full recharge cycle several times a week. I ride 3000 miles a year (4000 miles total) and wind and inclines are by biggest battery range zappers. We get spring winds with 15-20 mph sustained with 30-35 mph gust always from the west (my ride home direction). I also riding from 4900 ft at work to my home at 5450 ft with that headwind. I can sometimes use 60%-80% power just riding home the 6 1/2 mile ride home using PAS 3/4 at only 8-12 mph. I really haven't notice a big drop with cold weather; but, I have a Luna Cycle triangle battery cover and my ebike is kept indoors at work and home. I ran out of power about a mile from home once and the Radrover is one heavy bike to pedal above 4-8 mph without some level of PAS on any incline and/or headwind unless you are closer to tip/top shape. That was when I got the 3rd battery fixed and purchased another charger to leave at work top off for windy days.
A second battery would have the advantage of 2X your range, maintain your preferred cruising speed, and 3X or even 4X battery longevity because you are not hitting the full charging cycle several times a week. The $$$ I spend up front will hopefully breakeven or even save me money 3-5 years down the road in other aspects in my life (less wear/tear on car, better health, new hobby/friends, taken both Rads on vacation to Grand Canyon/Sedona, we now do family X-mas luminaria bike tours every year, etc...).
I only got around 800 miles from my rear kenda tires (a little longer from the front tires). Paved road commuting really wears down these off road tires. I switched to Vee8 26X4 120tpi tires and had an improvement in range, acceleration, traction, less flats, less noise, 2X to 3X longer tire wear, and lighter tires. You are going to have to change tires anyways around 1000-1400 miles. Doesn't hurt to start looking at replacements or have a summer/winter types like some do with vehicles depending on current road conditions, temps, and riding style.
The Vee8 can do everything the Kenda can do; just better: