First off, nice decision on using the Science Workbook! I thought it was one of the main reasons why I did so well on BS and PS. I would recommend you go through the discrete sections without timing and just use those for content review.
For the passages, it would depend. Sometimes I timed myself and see if I could finish a 7-question passage in like 6-7 minutes to push myself, while other times I did not even time myself. It all depends on whether you have been having trouble finishing the BS/PS sections on the AAMC practice exams. If so, then YES; take this opportunity to improve your pacing skills. But if you have been finishing with lots of time to spare (10-20 minutes) then by all means, don't worry about timing and just use it as a nice content review.
Trust me, it's one of the best things to use when reviewing all of the concepts. I mean, what better way to review than by practicing questions!?