In Jain cosmology, the maximum life span in the 7 naraks is generally given as:

1. 1st narak — 1 Sāgaropama
2. 2nd narak — 3 Sāgaropama
3. 3rd narak — 7 Sāgaropama
4. 4th narak — 10 Sāgaropama
5. 5th narak — 17 Sāgaropama
6. 6th narak — 22 Sāgaropama
7. 7th narak — 33 Sāgaropama

So, the maximum life span in the 7th narak is 33 Sāgaropama.

If you want, I can also give the minimum life span of each narak in the same format.