I don’t know how to split your script into multiple scripts, but do you actually need to run a script?

If you use Make’s automations & integrations to run your automations, the time limit is 40 minutes per automation.

Even better, you don’t need to know Javascript to use Make, because it is a low-code/no-code platform.

If you’ve never used Make before, I’ve assembled a bunch of Make training resources in this thread.

For example, here is one of the ways that you could instantly trigger a Make automation from Airtable. 

I also give live demonstrations of how to use Make in many of my Airtable podcast appearances. For example, in this video, I show how to work with Airtable arrays in Make.

Hope this helps!

If you’d like to hire the best Airtable consultant to help you with anything Airtable-related, please feel free to contact me through my website: Airtable consultant — ScottWorld

You cannot get around the limit of 30 seconds for scripting automations.

What does the script do, and what is causing it to take so long? 
If you are updating multiple records one-at-a-time, this example script by Airtable shows one method of updating records in batches of 50.

The script goes through each row to calculate a running total of what the consultant is to be paid out on each invoice, so the amount in the payout column is the threshold (as a negative) + all their splits. Acts as a running total for each invoice. 

One way to extend the time needed for a script is to break your script up into section and then string them together in an automation. Each script has the 30 second time limit (i think this went up to 120) but altogether you have a 5 minute limit. That's from memory. I wasn’t able to find this by searching on the web . . but I remember reading that somewhere.