I said they can, not that they will. If it is close to sold out, they obviously won't. If they still have a few unsold rooms, Amtrak yield management might reallocate some of them into lower buckets, as they appeared to do on the Empire Builder recently. They also may not be tracking all that closely in any given situation and ignore it, too.Interesting to learn that points for roommettes go down just before departure . I tried searching for today from NYP-CHI and it says 21,000 points.. It says "1 left at this price". So I guess to get 13k points there would need to be several unsold rooms, not one? And how far in advance will the points drop to lowest bucket ( the day of, 1 day, 2 days before departure )?
Although I did search today for Rochester to South Bend and it shows only needing around 12k points. This would be 11:30PM till 9AM in the roomette. Just enough for me to rest, shower and eat..
On way to gauge the odds of whether a drop is likely is to measure the inventory by doing a dummy reservation for up to 8 rooms. If a significant number of rooms show up and it is closing in on departure date, chances are good they will reallocate some to lower buckets, assuming they are paying attention.
Yield management is dynamic, Amtrak can reallocate at any time. There are windows where it appears more likely, based mostly on individual experience and anecdotal evidence here, but it can happen any time. No one can give you a formula like x days prior to departure = y bucket.
Finally, do all your research using cash fares and @niemi24s' charts. Most of us, including myself, don't have that good of a feel for point redemption values, even though most of my sleeper trips are on points. When you find a fare that you can see is in a low(er) bucket, then book it with points. Lower cash fare will be reflected with lower point values.