As someone who has changed usernames in the past, I'd say this, It's 100% your call.
I changed mine from my original username when I joined this specific SE and added a notice on my profile to let people, from other SEs who know me, know that it's same old me.
It's a feature provided to you by SE and you don't need community consensus or discussion to do so, it's your right. As long as you are not breaking any rules or violating any agreed upon policies or disrupting the site experience in any way whatsoever, you are free to do anything you want. E.g. Change your display picture all you want, but don't be rude to other members etc.
Technically, SE identification is via userIds (Which remain constant) and your associated emails. Nothing crucial in terms of identity is tied to your username.
However, as Mithrandir said, you shouldn't do it if you want people to remember you or associate you with a certain type of posts.
TL;DR, it is purely up to you.