EU may be “rich enough” to support Ukraine forever, doesn’t mean it will or should do it.
So European NATO countries basically need to keep supporting Ukraine while they try to becomes militarily independent of the US.
If Russia really becomes weaker and the war winds down a bit, then supporting Ukraine is likely to become cheaper as well. But as long as Russia manages to send tons of drones and missiles to Ukraine, Europe should be worried. So Ukraine will remain a testing ground for air defense for a while.
There is also the issue with the Baltic countries and to some extent Finland. Those countries are terrified that Russia will do something stupid.