Git new-feature-branch best practices

Hi all! I have a question about using branches.

For example, I make branch for some experimental feature. After some
time I have completed this feature. I'll checkout previous branch and
merge this new feature's branch to it.

And there is my question. If I know that this feature was implemented
very good and _will not be changed lately_, should I remove this new
feature branch (because it will be unused)?

Is there some best practice what to do in my case?

So, should I remove a branch for some new feature after its
implementation if I sure that I will not edit this feature's code later?

May be, there is answer for my question already and I missed it?