Just before departing from Passionless Valley after his first fateful visit there, Yeung Gor took a half dose of Passion Flower Poison Antidote from Kau Cheen Chek. Kau Cheen Chek then told him he would have eighteen days to live.
Obviously, thanks to certain circumstances, Yeung Gor was able to survive far longer than eighteen days, but just how much time passed between when he left Passionless Valley that first time and when he returned later - plus a Heavy Iron Sword, minus an arm?
Let's take a look at all the significant events that happened in between his first and second visits to Passionless Valley:
1. Traveled from Passionless Valley to Seung Yeung Fortress (stopping at Kublai Khan's basecamp along the way).
2. Spent a few days at Seung Yeung, but failed to assassinate Gwok Jing. Participated in several battles against Mongols.
3. Nearly gets killed along with Gwok Jing, but manages to rescue him with the help of Fung Mak Fung. Gwok Jing injured.
4. Wong Yung gives birth to twins. Mo Brothers duel over Gwok Fu. Lee Mok Sau arrives at Seung Yeung and kidnaps baby Gwok Seung.
5. Yeung Gor and Lee Mok Sau protect Gwok Seung from Golden Wheel Monk. In the midst of the pursuit, Yeung Gor encounters the Divine Condor and learns about Dook Goo Kau Bai for the first time.
6. Mo Brothers critically wounded by Lee Mok Sau. Yeung Gor sucks out their poison to save them, but falls into coma in the process.
7. Little Dragon Girl finds out that Wan Tze Ping was the one who ended her virginity. Pursues Wan and Chiu Tze Ging from Seung Yeung to Mt. Chung Nam. Along the way, she meets Chow Bak Tung and learns the Left/Right Hand Technique from him.
8. Thanks to the interaction of the Passion Flower Poison with Lee Mok Sau's Ice Soul Needle Poison, Yeung Gor survives and comes out of his coma. Is this the point that the original eighteen-day deadline should have passed?
9. Yeung Gor loses his arm.
10. Yeung Gor is unconscious some days. Divine Condor gives him snake organs, Heavy Iron Sword. Yeung Gor begins training in Heavy Iron Sword Technique and plotting revenge on Gwok Fu.
11. Yeung Gor, his martial arts greatly improved, attempts but ultimately gives up getting revenge on Gwok Fu.
12. Gwok Fu deals with aftermath of cutting off Yeung Gor's arm. Nearly gets her own arm cut off by her father, Gwok Jing.
13. Wong Yung battles and defeats Lee Mok Sau. Briefly reclaims baby Gwok Seung before she is taken by Yeung Gor.
14. Yeung Gor travels from Seung Yeung area to Mt. Chung Nam with baby Gwok Seung.
15. Chiu Tze Ging plots takeover of Cheun Jen Sect. Wan Tze Ping briefly becomes fourth Cheun Jen Sect Leader. Cheun Jen 5 Disciples develop new formation to fight Yeung Gor/Little Dragon Girl. Mongols attack Chung Yeung Temple.
16. Golden Wheel Monk, Little Dragon Girl injured during Chung Yeung Temple confrontation. Wan Tze Ping and Chiu Tze Ging die. Yeung Gor and Little Dragon Girl officially married.
17. Destruction of Chung Yeung Temple. Death of Gok Dai Tung.
18. Little Dragon Girl stricken by Ice Soul Needle errantly thrown by Gwok Fu.
19. Yeung Gor and Little Dragon Girl leave Mt. Chung Nam and head back to Passionless Valley. Meet South Emperor 1 Deng and Chi Yan (the former Kau Cheen Yan) on the way.
20. Return to Passionless Valley at last.
How much time passed during that whole sequence of events? It was definitely more than just eighteen days. Just traveling among these various locations would have taken weeks, and it must have taken at least a month for Yeung Gor to improve his martial arts so much after losing his arm. It would seem that at least two months went by.