The title thread thread is a stickied thread in Help & Questions. It need a tweak and a correction.
It should say "user dashboard" in place of preferences.
I went to the preferences link that I found on my own account, and there's no GA data there, so this must have changed when the UD was created.
Some items are not retired randomly. In particular Battle Coliseum Challengers retire in approximately one month and Monthly Collections retire in a month. Yes there often is a variation of a few days, but this doesn't seem "randomly" to me.
The first thing you mentioned about Preferences vs User Dashboard is kind of confusing in general.
The URL for the User Dashboard is subeta.net/preferences.php, while the link for the actual Preferences page is that same URL with "?act=prefs" added to the end. Not hard to lead to some confusion with URLs like that.
As for the second point, it's true that some items do have regular retirement schedules. But a lot of other things are usually just retired whenever staff feel like they have been around long enough and aren't being bought very frequently anymore, or whatever. Maybe the wording could be changed to not have "random" in it, but just mention that it varies for different items.