Is it possible to upload millions of records from CSVs in the file cabinet using SuiteScript?

Hello! I'm running into issues loading custom records called "Guides". They're a part of the Campus Stores package. These guides come from book publishers, and they specify how much money to give students for textbooks they bring us. There are issues though:

• there are three guides with ~700,000 lines in each
• we can only load 25,000 at a time
• each 25,000 takes 4 hours to complete.

Currently, we have a person that babysits these guide loads for a week straight, and this is their #1 priority. This is ludicrous though -- is there any way for us to bypass this? My thought is to use SuiteScript to load records from CSV files in the file cabinet 25000 at a time, but I wouldn't know where to begin doing that. We won't need to do this again for a few more months, but it'd be good to find a better way between now and then. Is there a standardized or best practice way