If you DELETE the branch after merging it, just be aware that all hyperlinks, URLs, and references of your DELETED branch will be BROKEN.
I prefer RENAME rather than DELETE
All my branches are named in the form of
Fix/fix-<somedescription>
or Ftr/ftr-<somedescription>
or Using Tower as my git front end, it neatly organizes all the Ftr/
, Fix/
, Test/
etc. into folders.
Once I am done with a branch, I rename them to Done/...-<description>
.
That way they are still there (which can be handy to provide history) and I can always go back knowing what it was (feature, fix, test, etc.)
Source: Stackoverflow.com