[HPforGrownups] timing of the p-stone defenses

[Odile Falaise]

No: HPFGUIDX 58846

Cassie theorized:
<<<I have my own theory. As far as I know, we don't
KNOW when the stone defense was set up exactly. We
know it spent some time at Gringotts -but do we know
for how long? The whole thing could've been being
planned long before Harry found out about it. >>>

And now me (Odile):
Cassie brings up an interesting point - we know that
certain teachers (plus Hagrid) set up obstacles to
getting the Philosopher's Stone, supposedly at
Dumbledore's request.

Fluffy was in place early in the school year - we know
this because HRH plus Neville ran into him, and then
Fluffy took a piece out of Snapes leg at Halloween
(October/November.)

What about the Mirror of Erised?  Harry found it over
the *Christmas* holidays - in December/January.  He
got busted by Dumbledore, who advised him that the
Mirror was going to be moved.

Why wasn't the Mirror in position in the first place? 
Did Dumbledore have reason to suspect something?  Was
Snape reporting his suspicions about Quirrell to him,
perhaps?  Or did Dumbledore (in MAGIC DISHWASHER
mode??) place it in that room know that Harry would
stumble upon it?

What do you guys think?

I doubt this is new - I would appreciate someone
pointing me to a/the thread that has addressed this
before, if such a one exists.  Thanks!  ^_^