Batteries degrade over time, I'm not really sure what else you expect from your phone.

There are steps you could take to improve the life of your battery, but I don't really understand the difference between the battery life being at 95% at full charge or spending the time of maintaining a charge level between 20% and 80%.

Just use the phone, if it doesn't last the day get an in car charger for it, or charge while you're at work.