Theoretically, storing closer to 50% is better. Practically, it won't make much difference. The cars are very consumer friendly and don't need to be babied too much, outside of avoiding battery storage at 100% or less than 10-20%. Other than that, do whatever's easiest for you.
I personally just charge when I'm done driving during off peak hours (or when the sun shines since I have solar). I will leave my battery at 80%-90% often. I have almost 40k miles on my 3 and degradation is in line with, if not slightly better, than comparable 3s.