Will filling out the Pinecone Inactive Message field affect recurring transactions?
When you set a Pinecone donation landing page to "Inactive", end-users will be unable complete a new donation but this will not affect recurring transactions that were previously set up on these pages.

Why does this matter?
Recurring transactions are important for a number of reasons. First, they allow our clients to have consistent cash flow throughout the year. This allows organizations to create more accurate forecasts and strategies around other fundraising avenues.
Secondly, recurring transactions are the best way to retain donors. It is significantly cheaper for organizations to retain their current donors than to go out and acquire new ones. Disabling donation landing pages will not affect recurring transactions that were previously set up, thus eliminating the worry about donor churn.
Resources
You can learn more about how to disable donation landing pages by following the steps in this article.