AAUP standards for timing of recruiting/resigning a faculty position: Do they really mean anything? According to the American Association of Union Professors (AAUP), 

A faculty member should not resign, in order to accept other employment as  
of the end of the academic year, later than May 15 or 30 days after 
receiving notification of the terms of continued employment the following
year, whichever date occurs later. 


...

An offer of appointment to a faculty member serving at another institution 
should be made no later than May 1, consistent with the faculty member’s
obligation to resign, in order to accept other employment, no later than May
15. It is recognized that, in special cases, it might be appropriate to
make an offer after May 1, but in such cases there should be an agreement by
all concerned parties. 


The few relevant comments in this thread

http://chronicle.com/forums/index.php/topic,163851.15.html

(e.g. comments 23, 26, 27) seem to indicate that this standard isn't important/widely observed. 

However, it appears that some universities do observe it (or some variant), e.g. University of Pittsburg and University of Louisiana and Lafayette. 

My questions are


Is this etiquette widely observed? That is, would this be a reasonable barometer of what is "ethical", or is the standard dated (if ever relevant), as indicated by the commenters in the linked thread above? 
should I let the existence of this AAUP standard modify the way I handle accepting a pending offer that would require me to go beyond this May 15th deadline?


I'm soliciting anyone with knowledge of these matters but information from deans, department chairs, or anyone who has resigned at this late stage would be especially valuable. Thanks for any info. 



Note: Previous posts of mine give a bit more (probably not relevant) background: 

I want to leave my tenure track position before fall. I have great prospects but no new position &quot;locked up&quot;: when should I break the news?

Proper &quot;notice period&quot; for resigning a tenure track position?

The second one is closely related but is distinct in that this question specifically is about observance of the AAUP standard that I learned about today while reading the chronicle. 



Note 2: Mine is an AAUP school but does not have any explicit policy like the two mentioned above.
I have seen faculty leave or take positions at all kinds of times during, before, or after the semester or even right after (or during!) sabbaticals.  The AAUP guidelines are nice, but, ultimately, everything depends on the schools involved.

If you are concerned about ethics, I would recommend being upfront with both departments (the one you are leaving and the one where you will be hired) and coming up with something that leaves both of them satisfied.