I was asking myself how many spam messages have I reported in a time period. While I know that the messages left in the "Held" folder are automagically deleted after 14 days and then they're gone for good, I though -without any reason, I reckon- that, If I deleted the spam after reporting it, it would last more in the "Trash" folder and I could know how many spam mails I reported monthly, but to my surprise, the messages in "Trash" folder are too auto-deleted after 14 days.

Are there any sort of "personal statistics" to track this sort of things?

Maybe. Sort of. See http://forum.spamcop.net/forums/index.php?...ost&p=24936 and following.