I've recently changed my Someday/Maybe list into 2 lists. A Someday list and a Maybe list.
In my mind, Someday means that I will do it when I have time, while Maybe means I might not do it but I just want to have a record.
So the process for me is that everything first goes to my Someday list first which I review in my weekly review.
During the WR, I will prune the list and move some items to the Maybe list (I try not to have more than 30 items).
Then every 3 months I will review my Maybe list and see if I want to move it back to my Someday list or Project list. Either way, I rarely delete anything.