I wouldn't go down to 150lbs, or you'll end up with barely inadequate muscle strength and Bone density.
Bearing in mind, you will lose those at a more accellerated rate, when you're over 50, so what's the point training hard for years, so you end up when your 75+, in potentially poor condition, moving badly, not in very good nick, with possibly only slightly better Blood Pressure, Cholesterol and aerobic condition, than slim guys who slobbed a lot for 50 years.
In the end you'll be a bit better off physically than most, but you'll still to some degree be cheating yourself.
Being 160-165, would be a much better option, if you're not someone like I'm not, that craves a massive physique. That kind of lean weight is not very massive, and still better than a rakish 150. Then at least you might end up by the age of 75, less conditioned, but about as well conditioned as you would be, if you stick to your current goal of 150 lbs, which is better than aiming for 150 now, and later becoming a guy who's about as well conditioned as an average 12 year old, who's forced by their school to move for 2-3x a week.
Once you get slightly above average old mans condition, to improve on it to any real degree, will be very much harder than having a bit better condition, and then spending years fighting to keep it.