Is it possible to limit this period or not?
The duration for which customers can download updates for a product they purchased in Magento Marketplace can vary depending on the product and the developer. Some developers may provide updates for a limited time, such as one year, while others may offer lifetime updates.
As a developer, you have the option to specify the duration of time for which updates are available to customers. When submitting your product to Magento Marketplace, you can indicate whether updates will be provided for a limited time or indefinitely.