Ok Syed. The we need to get some more information.
1) How many cubes are included in that create index variant
2) Are they full load or delta load or both?
3) How many hours it takes to complete the step and if you check in the job detail, you could even say for which individual cube its taking more time
4) Do you have history data in the cubes or just very recent data. If you have history data, you could get your business approval to delete them
5) Do you also compress the cube weekly. Are there aggregates build on them?
Regards
Karthik