If d pax files TDR after chart, it wil take its own sweet time and also, we hv seen here lot of complaints against "some TTE", selling tkts for UR / RAC pax for d pax not traveled.
There is no guarantee that TDR filed will b entertained 100%
And also even if TDR is approved, d refund will b only 50% of d tkt fare, which is very less compared to canceling d tkt