You must calculate your capital on that coin first, for example now the price has given you profit 30 % from your capital, i think that is good time to sell your coins. If you want more profit, you may wait for few days again. But, remember that the price can be bubbled anytime, try to satisfy with less of profit and not to be greedy.
Your Idea is not bad. I likes your Idea. Even I also Observed that the altcoins price are increasing last moments of every year. So, sometimes anybody can follow this instruction and can be profitable.