I am on the crazy side of the spectrum, currently training 10+ hours a week to do triathlon + powerlifting, but I think a more sane person could get a huge benefit in maybe 5 hours a week. 7 minutes will do something, but I would love to see any 7 minute a day workouter in as good of shape as a 5+ hour workouter.
I do disagree that the ideal workout is go to the gym and lift weights 3-4 times a week. Gym is good, weights is good (I do them), but cardio is also super good. Most studies about exercise makes your memory x% better, or exercise makes you live y% longer are about cardio.
Ways to try and get both?
a) 4 days of 1 hour of crossfit type exercise would work (not my preference) or b) 2 days of weights for about an hour, 2 days of cardio for about an hour, and a decent amount of walking on off days.