As the chart posted by E-Wheels shows, it's the last 20% of topping off your battery that shortens long-term battery life the most. If (I'm making up some numbers here) your daily commute knocks 8% off your battery charge, from 80% down to 72%, it's not going to make too much difference topping it back up to 80% vs. waiting until the end of the week and charging from 40% back up to 80%--I would be inclined to go along with rich c's practice of waiting several days just to avoid the minor hassle of recharging every day.
On the other hand charging from 92% up to 100% every day would be hard on the battery. It's when it's reaching maximum charge that the battery chemistry sustains the most damage that eventually limits the amount of charge it can take.
You can manage a less-than-100% charge cycle by figuring out how much of a charge it can take in 10 or 15 minutes to calculate a per-minute percentage boost. Then figure out how long you have to charge the battery to get the total amount of percentage boost you want to get to your target. Buy a timer that will allow you cut off power to the charger after the desired time interval has elapsed.