Jeff,
Forums all around the world are spammed in a similar manner every day, unless you manually approve all members there's truly no way of stopping it except by having a paid only site (lancerforhire I'm anticipating you posting here

j/k j/k). Some are human every now and then and can bypass even the most supposedly "intuitive" anti-spam systems. Something that everyone currently knows and if not should learn and bear in mind is, it's a never ending battle against spam just like cable rates rising each year

. Some have however found solutions or a combination of a few that work well together proving to suit their site better in regards to preventing spam.
Also the spam comes day by day as you said so we must address it day to day and can't foresee a spambot planning to join and post later that night in fact nothing available can unless your going by
IP and then what's to stop those in other countries who can simply unplug their modem and then it resets w/ a new IP from coming back? Again it's never ending but up to those who are site owners and admins to find a solution ideal for their site, I believe it's setup fine here and what gets in is tolerable considering the staff on hand who remove said posts promptly.