Apple is indeed encouraging update to iOS/iPadOS 18 for devices that support this major version - iPadOS 18.1.1 being the current release. iPadOS 18.1.x is very stable - and does not appear to have any significant issues.
While you don't have to update if you don't wish to do so, short of updating, you cannot suppress the available-update notification.
In all likelihood, Apple will no longer offer iPadOS 17.x updates for your iPad. Similar to the release of prior major-versions, updates to your existing installed version of iPadOS continue for a limited period - after which time updates cease to be available unless you update to the now-current major version. History demonstrates that this cut-off typically occurs late November or early December.
Also be aware that release of iPadOS 18.2 is anticipated to occur in the early weeks of December - bringing additional features and capabilities to your iPad.