The EU is rich enough to support Ukraine for a very long time. During that time it is likely that Ukraine develops better and better weapons. This requires Russian army to improve as well.
It's not clear how the Russian army will improve when the economy declines.
EU may be “rich enough” to support Ukraine forever, doesn’t mean it will or should do it.
The EU is rich enough but will they stay "willing enough"? Unfortunately, many EU parties that are gaining popularity are also against spending money on Ukraine