I vote yes, it just all depends really on if you want this as a PROFESSIONAL portfolio or not. In my case, I would LOVE to be able to afford to change my user name, but simply can't afford to. I think it would just instantly make my portfolio more respected to my viewer.
I don't think it's important on DA - professional artists and art directors don't really treat DA as a professional resource. It's well known that there are many professional artists that use it but it's not generally where you would host your portfolio that you would point clients at, it's more of somewhere to just share what you're working on and connect with people more easily than you can on say your own word press site.
I am actually more commonly known as "GTX" in both my personal and professional worlds. I don't find it odd in the least. All of my correspondence, though, contains my name AND my alias. Some professional contacts have even used "GTX" in greeting me at conventions I photograph at, and typically I seem to respond faster to "Hey G!" or "Hey GTX!" than I do my own name XD.
I have changed my name on here once. It used to be "GTXCrusader", which was typically just an online gaming alias I used. Once I got into photography, I liked the name of "GTX", but adding "Crusader" didn't sound right at all, thus it became "GTX Photography" for all my photo work, and once name changes were allowed on DA, I changed it.
In the future I may consider changing yet again to "GTX Media", as I'm now expanding into video production. We shall see, though...
This isn't a question you should be asking. Changing your username is something that will affect you and you alone, your watchers will tell you not to change it because they're used to the current one and are scared of change.
You should do what you think is best.
But If you have to ask, I'd say a that a different username would look better. Honestly when I hear "keep walking" I think of alcohol, and having a number last on your username makes it look a little childish and gives the impresion that you went for an overused username.
A lot of people have a dual profile. One for more of their personal life, and then the professional one you put on business cards and in signatures. You can choose to have them inter-connected, or even a one way connection to where people who have your personal profile can click through to your 'work' one.