Elegant and fast way to join all string sequences

I want to do what title says:

{"a","b",1,2,3,4,"a",2,2,2,"edg","?"} => {"ab",1,2,3,4,"a",2,2,2,"edg?"}

in the most elegant way. For example one replacement rule for ReplaceAll.

I have manage to do this:

test = {"a", "a", 1, 2, "A", "b", 123, "a", "end"}SplitBy[test, Head] /. {x__String} :> StringJoin[{x}] // Flatten

{"aa", 1, 2, "Ab", 123, "aend"}

But I find this way inelegant. Could You help me with creating good pattern?

Edit

Bonus request: It should be comparable in duration.

Also there is not need to do this via pattern-matching.

Conclusion:

There are many great answers. Each one is educational and worth an upvote. I should now accept one, the problem is I have not stated this question's goal so clearly, my fault.

• rm -rf's is the fastes and the shortest however,
• I decided to accept Jacob's answer as the fastest one and because it seems it has not focused attention as it deserves.
• Yves Klett answer fulfill my need of a single pattern solution.

As Mr. Wizard pointed out one could think I should accept rm- rf's answer. One could also think Yves Klett should receive it as his answer fits my primordial need.I will abuse a vague form of this question to give them a bounty insted.