What is the balance for a good performance to import supplier objects?

Summary:

Normally import jobs use to have good performance until they reach certain number of records to process, over that threshold the jobs require more time than usual to perform all the operations and in some cases they finish without processing all the interface records. I would like to know what is the maximum number of records (e.g. 20k records) to import supplier objects (header, address, sites, etc.) with a good performance. Thanks.

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