I don't have any paysites, so take this with a grain of salt. I assume surfers want regular updates. If you do do unscheduled updates, do multiple a day. People will keep checking back for them.

I know my favorite places to go, I am constantly checking to see if something new is posted. If you have an update schedule, STICK to it, and have it regular. Such as 9am 6 days a week. It should be fairly easy to do with scripts. Input a week's worth of updates into the script at a given time, and let the script automatically add and inform the users of the updates at a regular scheduled time, so if you get the flu or are out of town, the site is still updated. It should retain members the best if you have daily updates, no matter what, and INFORM your users of what is updated.

ZoiNk