I never said the RE up market was rational. In fact, buying is very much emotion rather than logic or else all the fundamentals everyone quotes wouldn't be so out of wack. People tend to buy because of needs/wants rather than financial ratios/forecasts, etc.
I don't think anyone has a clear idea on how much this upswing in the market is being generated by first time buyers and upgraders versus speculators. If you do have some reports, please do share, my personal view at this time is most of the activity seems to be the owners upgrading their homes.
And if your neighbour sold for $300k when you bought for $500k, are you going to say "Oh noes, i better sell at $250k while I still can!". If your neighbour sold at 700k, are you going to say, "hmm I better sell now and make 200k". Probably not, unless its part of the normal life events you stated which I don't disagree with you about.
Normal life events will happen, people will buy and sell RE at whatever the current price but my belief is that the majority of recent demand has been from owner occupied sales whether from first time buyers or previous owners now upgrading. Not all of them have overstretched finances and not all of them will trample over each other to sell once the market starts to fall.
The market is in store for a correction in the near future but I doubt it will be the bloodbath that some people suggest here and if that gets me labelled as having "bullish" ideas, then its pretty funny

