For those who are not using lifetime listings... how do you announce your existing customers that their listings is about to expire ? ( maybe some would like to renew... ) if you... ?
How can you say that they will not renew ? We have directories offering permanent as well as yearly listings, and the one with yearly listings people do subscribe as well as renew after there link expiring.
If you don't notify them via email, I doubt you will get many renewals as many are probably not keeping track of the subscriptions themselves. I email folks. Depending on your site, you might even want to include some statistics to help make the sale.
Not everyone uses phpld so dargres mod is pretty useless unless you do. If you use Paypal you can set that to notify people if they are on an annual subscription. As YMC said, e-mail is always the way to go and it doesn't take a lot to integrate this into a script so that it automatically does it for you.
You might be surprised. Some of them might renew and you could get some $ from this. On the other hand...having permanent listings can make you to lose some $$$. Nobody would like to get listed on the 5th page on a category in my opinion.