When Gwok Jing and Wong Yung stalled the Mongols long enough for Genghis Khan to die at the end of LOCH, the Mongols were forced to delay their invasion of Seung Yeung Fortress for about eighteen years.
After Yeung Gor, Little Dragon Girl, and various allies routed the Mongols at Seung Yeung and at Mt. Chung Nam, the Mongols' plans were delayed for sixteen years.
After Yeung Gor killed Mongke Khan and Gwok Jing and his allies counterattacked the Mongols, Seung Yeung remained safe for thirteen more years.
18 + 16 + 13 = 47
47/3 = 15.66666
Ergo, heroic actions plus lucky breaks (death of Mongol leaders) gets you an average of 15.6 more years of freedom for Seung Yeung Fortress.