It's all depending on your own preference and what you're growing for..
If you're growing to smoke, and want an energetic high, then don't wait for amber.. Go for milky/cloudy trichomes only.
- If you however want to get stoned, then go for amber trichomes. The more amber, the more stoned the high.
- Clear trichomes don't posses much THC, so should be avoided if you want a high at all.
You can mix milky and amber as much as you want, depending on how much of a stoner you want your smoke to be.