My provider is astraweb, retention i think is 65days. When i 1st down loaded alt.binaries.games.xbox360 it took ages and dispayed all 65-days, after i logged on again and updated all i see is the last 14days.
there maybe a setting that only downloads the threads that you aint down loaded before. for instance if you first updated it 14days ago then it would download all the threads, then if you update it after this it wont download the threads you had previosly downloaded. i dont use the same program as you but, i have seen this on a few programs.
anyway, dont waste your time by updating the threads all the time, just use a nzb search engine like this