I think you're right about the repetition of a note. But as I understand it, you can't come back to that note before the full tone-row is completed.
I'm not an expert, and maybe "dodecaphonic" is different (a broader term) from Schoenbergian 12-tone serialism.
There's good reference here...
http://en.wikipedia.org/wiki/Serialism
... but no specifics as to the restrictions on note repetition. (But clearly it's a lot more complicated than just how you use the 12 pitches, eg, rules on use of intervals, and other musical aspects to which serialism can be applied. )