Countries will get fed up of sending aid to Ukraine long before Russia decides to return its annexed territories. We're already seeing signs of that.
If NATO isn't willing to go in and force the Russians out themselves, I fail to see how this war is anything but a net gain for Russia. They will just sit back and let their "new territories" become more and more Russified.
To me, the aid is just a delaying tactic to allow Ukraine to continue fighting until the west can figure out a way to accept that Ukraine has lost its territories without losing face.
It's a shit show, but I don't share the optimism that a lot of people have for a Ukrainian victory. It's like a game of chess, and it's currently Ukraine/NATOs turn, because the Russians are already dug in.