Is it permissible to delay combining the prayers when traveling a distance of more than 80 km and returning after the Asr prayer?

Combining two prayers is a concession for the traveler. Thus, it is permissible for the traveler to combine prayers by performing the earlier prayer first (jama’ taqdim) if he departs after the time for the first prayer has begun, and to combine prayers by delaying the first prayer until the time of the second (jama’ ta'khir) if he departs before its time has begun. If you intend to return or stop at or before sunset (al-isfirar), you may delay the combination. However, if you will not return until after sunset or cannot estimate your return time, then you should perform each prayer at its own time, and the combination will be merely nominal (jam’ suri).