I've been using my old 10x50 (S/H) Nikons for the last 15 years and still find them good for me at 60. Just bought a pair of 20x80's but that was more for the bigger light bucket than anything else
The Nikons exit pupil is 5mm and I think the 80's are 4mm which still suits me fine. 10x50's will give you many years of use starting at late 30's and they are lighter for hand holding than the bigger aperture bino's.