There is no exact rule. But I think the best way to approach this question is the following:
You must always have analyzed the trend just above the "timing" in which you make your trading decisions. That is, if you are going to trade on a daily basis, you need to do it in favor of the weekly trend. If you are going to do it on an hourly basis you need to do it in favor of the daily trend. And if you are going to do it over 5-15 minutes you should do it in favor of the 1 hour-4 hour trend.