In case of upgrading the OSS by upgrading the product, you need to publish the new version of the source code as well as the source code before the upgrade on the web. The period of posting the source code on the web is different for each version of the product.
As long as you're offering your product, you need to keep your source code posted on the web.
In addition, the terms of the license may stipulate that the product may be posted for a certain period of time after it is no longer available.
If you are posting on the web, make sure you can maintain this appropriate response.