Take a look at the weapons system that the Mirage iii/v deploys and then we can talk.The replacement for PAF's mirages is not another Mirage, but a Delta wing platform with Canards. That leaves you with the J10C if you want something mature now, or a new home grown variant as part of Azm..... the other options are Rafale, or the Gripen..
Mirages have served their time very well for the PAF and it is now time to put them out to pasture.
Given how many times PAF/PAC has re-built these Mirages, repaired them and the facilties that it has to support the Mirages, if PAF valued them "soooo" much, then why have they not build brand new airframes to continue the usage of this platform into the future ?? It is simple, even they see the end of the utility of this platform and are actively planning its replacement.
Since the Mirage 3/5, the French have built the Mirage F1, Mirage 2000 and the Rafale as replacements for that lineage. That is how old a design it is ..