lithium ion batteries have come a long way since the first time they were included in a mass marketed cellphone. i can still remember very vividly that my parent's Motorola Microtac came with a battery discharge accessory to "deplete" the battery first before actually putting it on charge.

just charge your phone whenever you want, wherever you want and for how long you want and whatever harm that it may cause, it will definitely outlast the functionality of your phone.