First off: Congratulations on the score. 670 is quite high and there are a lot of people who would love to get that score, especially only studying intermittently. It's nice to take a second to be happy about your score, it helps to put everything in perspective.
Secondly: Only you can decide if you want to retake it or not. If you think you can hit 700 (or more), then you might feel happier taking it again, if only to see how high you score this time around. Of course, if the school you want to go to will gladly accept you with a 670, then it's counterproductive to spend your time on taking the exam versus something else. The only goal on the GMAT is to get the score you want. If you have that score, then you're good to go. If you don't, then consider the implications of taking the exam again on your finances and free time, and then make the decision for what's best for you.
Good luck and congrats again on the score!
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