I'd suggest Tiger Tim's questions are in a general sense, legitimate enough, and as I said in the P-40 thread it's foolish to be too dogmatic about how such 'buried treasure' scenarios are likely to turn out. Over time, what we see as minor factors have a cumulative effect, and not least, how something was originally 'preserved' will obviously have a huge long-term influence.
The two cases to consider is the 'Miss Belvedere' 1957 Plymouth Belvedere, familiar to most here, but for a recap:
http://en.wikipedia.org/wiki/Miss_BelvedereThat we can regard as essentially a failure, particularly given that it was 'just 50 years' and 20C technologies of preservation potentially enabled better preservation than we got.
Now imaging an equivalent that is not just a few times longer, more successful and historic, but literally
thousands of years earlier and a
successful essentially complete (if not 'serviceable') preservation of a vehicle. That's the Cheops or Khufu ship from over
four and a half thousand years ago!
http://en.wikipedia.org/wiki/Khufu_shipThose serve well as two bookend parameters of achievement and potential possibility.
As to 'buried crated' aircraft? Could be a huge variety of variation, as illustrated above. However tales of careful packing and securing of the machines for long term preservation are usually good modern publicity and if you think about it, hardly particularly likely at the time of placement.
These stories almost always prove a variable degree of disappointment; but, just sometimes, the Pharoh's technicians do good.
Regards,