The EU, well NATO has the problem what Russia will do when it is no longer at war with Ukraine. There is also the question what the US would if Russia attacks a NATO country.
So European NATO countries basically need to keep supporting Ukraine while they try to becomes militarily independent of the US.
EU just needs to support Ukraine until Russia has dug themselves into a hole that will take generations to recover from. Their might be a point where the war hasn't ended but Russia is no longer seen as a threat by the EU.
One issue is that Europe got caught with it pants down. It likely that Europe will keep improving its defense long after it is no long necessary from an economic point of view. Supporting Ukraine in destroying whatever Russia manages to produce is a sound strategy in this context.
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.
So European NATO countries basically need to keep supporting Ukraine while they try to becomes militarily independent of the US.