How long do you wait before deleting users awaiting email confirmation?

[محروم.كوم]

My site has approximately 40 members who have registered but are still showing as users awaiting email confirmation. I check the number of users in this category every few days, and I immediately delete any spammers or junk (with registration names like "lmno234" or email addresses like "[email protected]"). I perform random checks on IP addresses/email addresses/user names using StopForumSpam's database on the remaining users in this category, and rarely find any that are known spammers. However, some have been in this category for quite some time... close to a year in some cases!

So I'm just curious, how long do some of you wait before deleting users who are awaiting email confirmation, but who seem to never actually confirm? __DEFINE_LIKE_SHARE__