Are there any limits on the number of label merges that can be performed?

This article details the limits associated with the free version of Avery Label Merge add-on and the limits imposed by Google on Google Docs usage.

Avery Label Merge Limits

*Subject to Google-imposed limits (see below).

Google Limits

When more than 100 pages are merged into a single document, errors may be  result as Google Docs is not designed to handle huge content. This is why merged document sizes should be kept below 100 pages. Filter and track rows to know which labels have already been merged and which labels are yet to be merged.