Other Solutions
In some cases, changing the merge parameters might not be the best solution for your system. For example, if your merges are taking a very long time due to slow disk drives or other system contention, addressing those issues might do more to help your merge times than any amount of tuning can do. Also, if your merges are extremely large, it could be that the forests are larger than optimal. There is no fixed maximum size for a forest, but experience in the field has shown that when forests grow over 512 GB, query performance tends to start to decrease while merge times tend to start to increase. If your forests are larger than 512 GB, consider breaking them into multiple forests.