Double shifts would make little difference if you don't have more tiny cleanrooms. It takes roughly 8 days for each batch whether people are working one or two shifts. Add EDEN and everything changes, but even then it takes 8 days in the EDEN unless they've been able to shorten the time. Add a lot of EDEN's and then 24/7 manning may become necessary to keep them producing optimally.
I believe the Advent remark about working two shifts may have more to do with the completion of the new larger cleanrooms than production of DCVax-L.