I would not buy Polkadot (or any other coin/token) while the market is going up. If I had to do it while the market is rising it would be because I am going to keep those coins for the long term without being scared by the rise and fall of prices. Polkadot is a rising coin, but as good as it is, we must remember that it is not excluded from market conditions that affect any other project. We must also remember that a bull run like the one we saw a few days ago can be only for Bitcoin or for the entire market, that would also affect the price of Polkadot.