We use aMember to control access to some of our pay sites. One thing we noticed is that occasionally we'd get a call from someone saying that they say this error message when they tried to confirm their email address:
Incorrect link – make sure you copy link from your email client correctly
After a call to tech support it turns out those confirmation links are only valid for 10 days. By deactivating the code that checks the age we've been able to "fix" the problem. Here's the code from signup.php
Commenting out this code made it so that old email confirmation links worked. The only troubling thing is that a comment in the aMember code says that the check is there to to avoid code guessing. But, with our low-traffic site I'm not too worried about it.