Minor software updates are free. For the PC version, you can check for new updates using Help, then Check for updates under the main menu. For the Mac version, please visit the product page and download the latest version and overwrite the current version.
The PC version supports "rollback" to the previous version if you updated and found some issue and would like rollback.
Overall, if the converter is working fine for your files, there is no need to update if there are no issues.
ProperSoft converters are updated based on the customer feedback. Some converters are updated frequently, for example, weekly and some are updated less frequently.