The more time goes on, the more it seems like this is being deliberately slow walked as official strategy. Just as with the HIMARs and tanks it seems like a measurement of risk and capability. The US waits for confirmation of facts on the ground like continued Russian incompetence then slowly escalates. And it really seems like the final step is Crimea. If Ukraine is about to take Crimea, all of a sudden you move up the HIMAR positions and tanks...then you add air support and Russia is kind of in a checkmate situation.
That doesn't mean they officially give up and end hostilities. Certainly not with the (unlikely) prospect of Trump returning to the White House after next year's election. But you can certainly see how Russia could essentially be contained by some point next year, and if Crimea is taken what can they do? Enlisting more men becomes less and less valuable as the toll becomes more present in Moscow and social unrest grows. Then there's the issue of enlisting men just to throw them into artillery. You can't do that forever.