Your owner's manual will provide specific guidance as to the best approach to charging for your specific vehicle, but as a general rule you should only charge the battery to its maximum capacity when it is absolutely necessary. Battery lifespan is mostly dictated by cycles of charging and discharging, so the more cycles occur the shorter its lifespan. Charging to 80% capacity is usually the optimum level for longevity, but of course it is also important to charge sufficiently for the distance you plan to travel - if you have several days of short journeys and enough capacity to complete them on the current level of charge, it is better to do this than charge every day.