My hand is up and waving, mostly because I still remember two times in my life--once for 20+ years, then once again for 6 months--when I experienced "enough."
What "enough" meant and still would mean to me is a relationship in which the longing for each other never ceased. The awareness of being one half of a two-part being never left me. Remembrance of the last time and anticipation of the next time fit so seamlessly together that it felt like we were always making love.
At 70, the fire has cooled a bit. What I miss and yearn for now is less the heat and the release, more the kisses, endless conversation, skin-to-skin connection, and joy of waking up together. That would be enough.