Clamshell mode will ruin my battery?

I use clamshell mode. This mode require to keep the MBP plugged in all the time. This will ruin my battery? Do I should with to normal mode?

Context: I use a 4k screen primary screen and a 2nd 1080p. I always thought that I am saving screen life by using my to monitors and occasionally on the road use the MBP screen. Nevertheless, this is not the main reason for using clamshell mode, it is just because my 4k monitor it is bigger.

Thank in advance.