Russia is building more, so they will never fully run out. If you are thinking of storage, then they are out of the long range systems and currently move towards WW2 era guns. They have a lot of those, but the range is much shorter. So even more destroyed guns.

Nobody who has been following data (including satellite pictures) has said anything for a while that I can find. I assume government spies have good information but they are not talking.

About a year ago the predictions were late this year, or early next year. At the time Ukraine was typically getting about 60 artillery per day, for the last several months it has been around half that most days. Is this because Russia is better at protecting artillery and so it will last longer, or because they are seeing the end is near and so not using as much - I have no way to know.

If anyone knows of a source of information that is reasonably accurate who is talking let me know. I don’t follow many such sources, but generally the sources I do follow will report when others share useful data.