Google limit on spreadsheet script is set to around 6 minutes / execution. The more data you have to process the longer document generation will take. For example, converting generated documents to PDF can take more than twice as long as generating a Google document.
Note also that Google has strict limits for @gmail.com users and newly created G Suite accounts.
Google Apps Script current quotas and limitations: https://goo.gl/cbfe44
Gmail sending limits in G Suite: https://goo.gl/nUfdLx
Quota limits: https://goo.gl/pJm4JI
If your document generation stops at 50 you have 2 choices:
1. Click GENERATE again and again until you get all your generated documents. Our row status management allows you to run the process as many times as necessary.
2. Choose the option GENERATE > Every hour. This will allow you to do other work and come back when Doc & Mail Merge has finished generating your documents. If you close your computer while Doc and Mail Merge is generating your documents every hour, don't forget to refresh your spreadsheet when you come back to see all your generated documents.
NB: The script will scan each row during document generation, including rows that are already "done". If you have 1500 documents to generate, document generation will slow down the further the add-on gets down your spreadsheet. For this reason we recommend that you have no more than 500 rows per spreadsheet. To generate 1500 rows simply generate from many spreadsheets. Your Pro subscription to Doc & Mail Merge allows you to activate the add-on from as many spreadsheets as you want.
If you get a message "DoneFile not created" when generating from many spreadsheets simultaneously, delete the wording "DoneFile not created" and your document will get generated the next time Doc & Mail Merge is running.
Time-driven triggers cannot run more frequently than once per hour. See limitations set by Google here.
Contact us at firstname.lastname@example.org if you require a custom built add-on with specific requirements.