Number of Years Teaching at Hogwarts -- ?Significance

[ellejir]

No: HPFGUIDX 72436

I was listening again to the audiotape today and was struck by how 
much detail there is in the passages in which Umbridge interviews the 
teachers about their positions at Hogwarts.  She makes a point of 
asking each teacher how long they have been at Hogwarts. 
 
Trelawney said 16 years--significant obviously because of the 
prophesy she made 16 years before.  Dumbledore clearly wanted to 
protect her (and the prophesy--possibly in her memory) from Lord V 
and the DEs, so he kept her at Hogwarts despite her minimal skills as 
a teacher.  
Snape said 14 years--so he apparently came to Hogwarts around the 
time or immediately after Lord V's attack on Harry and his family.  
This timing seems very significant.  Do you think that he was on the 
side of the DEs or acting as a spy already for the Order at the time 
of Harry's attack?  Do you think that he might have had anything to 
do with Voldemort's choice of Harry and the Potters (vs. Neville and 
the Longbottoms) as the ones to attack???  That could explain some of 
his conflicted feelings about Harry.  
McGonnagal said something like 38 years (sorry, I don't have the book 
here).  Does this just indicate that she is an "old-timer", or does 
that number have other significance?
                                Elle