The Mercedes Me eco coach app gives the manufacturers advice on charging, parking and more, saying the charge level on parking has more effect on battery health than anything else. It recommends charging to less than 80% if parking for more than 24hrs and not parking for more than 10 minutes with 100% charge, so if you are charging to 100% at home for a long trip the next day you should be setting your charge point to complete charging at your departure time. This has the added benefit of setting off with a warm battery which helps achieve the best range, setting preconditioning for the same time also gets the cabin warmed by mains electric rather than using the car battery.
It’s generally not a good idea to charge to 100% while on a journey unless you need to as the charge rate drops as the battery gets near fully charged ( some cars take longer to get from 80% to 100% than to get from 30% to 80% ) and it’s quicker to move on at a lower charge and charge again later, rather than tying up a charge point others may be waiting to use.