Inconsistency on the speed during Increment migration

Hi,

I am facing some issues in inconsistency on the speed during Increment migration.
For example,
1. A 10+ GB site took 42 mins for incremental migration in the 2013 environment and took 52 mins in the 2016 environment. However, It took 2 hrs 58 mins for full migration in the 2016 environment from 2013.
2. A 20+ GB site took 55 mins for incremental migration in the 2013 environment and 56 mins in the 2016 environment. However, It took 4 hrs 45 mins for full migration in the 2016 environment from 2013.
3. A 40+ GB site took 9 hrs 10 mins for incremental migration in the 2013 environment and 9 hrs 53 mins in the 2016 environment. However, It took 10 hrs 12 mins for full migration in the 2016 environment from 2013.
Can you please help share thoughts about this is it normal or taking more time than usual?

Also, is there a way, a configuration or something to be done on Metalogix to speed up the migration process? Please help me out. Thanks.