Just floating an idea out there.
Normally most spam accounts created on here are easy to spot - they contain something obvious or the name is nonsensical enough to know that its spam.
But other times, its not so obvious. Here, either the account can be allowed and then at somepoint it might start to spam away, or worse be a "test" account to see if the site actually carries out any deterrence to remove spam accounts. Leaving it will give the green light to spammers to create more spam accounts.
The other option is to delete hard and fast, hoping that if a genuine account is accidentally deleted, the genuine account holder will create a new account and potentially kick up enough of a fuss for that to not happen again.
I follow the latter but still this leaves a lot of dormant accounts - accounts created where no one has posted, but have been sitting there for years.
Should there be a new policy in place to delete all old accounts if there has not been a single public post in the first 7 days since creation? (public posts, because checking other stuff like if private messages have been sent should be avoided.)