You should always worry about yeild more than potency as one hand generally shakes the other. BUT, there are definitely areas where I wouldn't mess around trying to get max yeild over potency and one is the flowering period. If those trichomes look pretty good at say 65 days and you let them go until 75 days you will have made a general newb move of missing the harvest window.
The plants will tell you what to do, not your own feelings, hopes, dreams or aspirations. Generally the plants stretch for the first 1/3 of flowering. Your plants did not take an unusually long time to finish that stage and they look at least 2/3's of the way done now. If they went 75 days I would worry a bit about having bud that's just narcotic and annoying to smoke. You'll wonder why you just get tired and never high off your shit.
Just plan for 65 and let it go an extra days if need be. The plant will eat itself for the nutrients it needs to continue. I always plan my nutrients as though the plants will take 65 days and if they take longer, they take longer and stay on plain water (or water with molasses) in the case of soil.
It's better to have them flush too long, than to feed them nutrients too long and have to harvest unflushed buds.