1) How busy the hotel is and points being available are often not connected at all. Poster above did not mention points anyway.
2) Suites showing open also does not mean they are sold. TONS of hotels hide the suite inventory to avoid DSU use.
3) Yeah if a suite is a very important thing, DSU are best to use IF they are showing open when you book.

Come back later when the hotel is not inconvenienced by you being a supposed "top" customer where they have to be troubled by offering you the treatment you supposedly earned through your loyalty.
My experience there was that it is fine enough and the breakfast I had was very good (years ago) but overall it is not that impressive and I would not stay there again either.