How strict are paper revision deadlines? I recently received a "revise and resubmit" decision for a submission to an Elsevier journal, and the deadline to resubmit is in about 5 weeks. Since I have to consult with my coauthors for my revision, and one of them is a professor who's not exactly fast in replying emails, I'm worried whether I'll be able to get a revision ready in time.

Is the resubmit deadline strict? Once the deadline passes and I don't make a resubmission, is the paper immediately rejected? Is it usually possible to ask for an extension?
The strictness of the deadline strongly depends on the journal and the context of publication.  For most papers to most journals, there is potentially a great deal of flexibility (assuming that you ask early and are polite about it).  The main exceptions that I have encountered are:


High-impact journals sometimes expect you to drop everything else on their behalf, and thus may give both a short deadline and little flexibility.
Articles submitted for a special issue sometimes need to hit particular dates in a production schedule, and thus may not have much flexibility to give.