Are there any limits on the number of label merges that I can perform?

Avery Label Merge Limits

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

Google Limits

When you merge more than 100 pages into a single document, you may run into errors as Google Docs are not designed to handle huge content. Hence, we suggest you keep your merged document size below 100 pages. You can filter and track rows so that you know which labels you have already merged and which labels are yet to be merged.