It is kind of unclear to me where you live. I'm guessing you live in Lahore and visit Mianwall for 12-13 days each time?
If so, the rule about praying qasr is when you are traveling for a maximum of 17 days:
It was reported from Asim, from Ikrimah, from Ibn Abbas (RA) that
Messenger of Allah (PBUH) stayed 17 days in Makkah & he shortened
prayers. Ibn Abbas (RA) said: So whoever stays 17 days should shorten,
& whoever stays longer should pray the complete prayer.
Also, it is important to distinguish when one is "technically" on a journey. Wherever you live, or wherever one lives, once they leave their place of residency, they are technically on a journey. It is well established by ahadith that the journey starts when a person starts from his / her place. And the journey ends only when he / she reaches back his / her place. So, if any of us undertake a journey, where Salat Al-Qasr is permissible, it is applicable right from the moment we leave our homes, and we can pray shortened prayers till we reach our home back (source).
So what is the distance where something becomes a journey? Some say 80 km away from your home (source).
Please note however, that some scholars vary of the number of days in which one can pray qasr. I personally have seem some say from as less as four days ("If you are going to stay more than four days you should offer your prayers in full" - source).