https://github.com/steemit/steem/blob/dd86ddecf99ec238bc7e3a3a40c53e12f017d782/libraries/chain/steem_evaluator.cpp#L712-L721

u256 w(max_vote_weight);
               static const uint64_t  vote_curve_window_sec  = (60*30); // 30 minutes;
               static const uint64_t  vote_curve_window_sec2 = vote_curve_window_sec * vote_curve_window_sec; // 30 minutes;
               auto delta_t = std::min( uint64_t((cv.last_update - comment.created).to_seconds()), vote_curve_window_sec );
               w *= delta_t;
               w *= delta_t;
               w /= vote_curve_window_sec2;
               cv.weight = static_cast<uint64_t>(w);

maximum profit in 30 minutes-time post