Half.com regularly runs speical offers to *new* users such as:
- Free Shipping
- $5 off a $20 order (or a related deal)

Do you know of any dates/events in the future in which Half.com is
expected to offer similar deals for *existing* users?

They currently have a deal where you get $5 for referring a new customer:

http://half.ebay.com/account/promo/ptb/ptbmain.jsp

Thank you for pointing out the $5 refer-a-friend program.  
As explained in the question description, I'm looking for information
relating to future savings offers for existing members.  (Basically,
I'm planning to buy 50+ books, totaling several hundred dollars - and
would like to know if it is worthwhile to postpone the purchase)

Best regards

All offers from Half.com to date have been for new users. Most
websites use simplistic methods to tell if you are new or not, and
often erasing cookies and changing your email address is sufficient to
become new again.

The best offer I have seen from Half.com is $15 off purchases of $50
or more. They don't usually have percentage based offers.

These are typical codes from the past that you enter during the
checkout phase:

WHENU33 - $3 off your first-time purchase of $5 or more
TEXTBOOK22 or FLORIDA - $15 off your purchase of $50 or more
BOUNCE - $10 off your purchase of $50 or more Expires: 30-Dec-2001
SCARECROW - $10 off your purchase of $50 or more
SOFTWARE or SAVE5NOW or WEBBUYS or SPEND - $5 off your purchase of $15
or more

These might be current, because there was no expiry data associated
with them when I found them:

HARRY - $5 off your purchase of $20 or more 
WINTER2003 - $15 off your purchase of $50 or more 
WINTER - $5 off your purchase of $10 or more 
SEMESTER - $15 off your purchase of $50 or more 
VISA33 - $5 off your purchase of $25 or more 

I would expect that $15 off is the best you will manage in the future.

Thanks for the info...
I'd rather not re-register - I have an extensive WishList in my
account.  Any information about discounts for current uses would be
much appreciated.

I have been using half.com almost since its beginning, and I have
never seen discount coupons that were valid for existing users. Nor
can I recall any "free shipping" deals.

You can, however, save quite a bit on shipping by purchasing multiple
items from one dealer:

http://half.ebay.com/shops/shippingDiscountsPopup.jsp

I've been using Half.com since it's inception; there have been offers
directed for existing users.

Anyone have any inside information?  Or, is it just best to close the
question at this point...

Thanks!