I am not sure what my number would be exactly to start to consider the bullrun might be over.  Perhaps if the price dropped below the 100 week moving average and stayed there for a day or two or even longer, I might start to get worried. Right now the 100 week moving up and it is about $74k.. so yeah.. maybe dropping into the $80ks (even the upper $80ks) might start to get me worried about the bull run potentially being over. It is hard to imagine such a scenario, but surely it could happen.

For me, even a test of $100k or a drop below $100k would not be enough unless the BTC price started to be persistently staying at those levels or lower.  Maybe i am too biased towards our being in a bull market, until we aren't.