I would harvest. Cloudy trichomes = peak THC. I would never harvest with more than 15% amber trichomes, but it's all personal preference. If you want a couchlock high, it's better to get a good indica strain and harvest it at peak potency (mostly cloudy trichs). Rather than let the THC (cloudy trichs) degrade into CBN (amber trichs). Unless you're just looking for bud that will put you to sleep.
I harvested one of my northern lights grows with 50-60% amber and I was very disappointed with the high. Next time I harvested at 90% cloudy, 10% amber, and it was some of the best bud I smoked.