The problem is heat, not charging speed. A wired charger heats the phone less than a wireless charger, and a slow charger heats it less than a fast one.

It's not like wireless charging will literally destroy your battery instantly, but it WILL do so faster than wired charging at the same speed.

You could offset the heat by charging even slower via wireless (easy with something that has a small battery to begin with, like a watch) but no matter what method is used, the one that runs the battery the coolest WILL last the longest, whether the difference is just one year out five, more, or less.