I am seeking survey results or statistical evidence pointing to the
value that actual or potential customers would place on a earlier than
expected delivery of a retail product purchased over the Internet or
via a catalog?

I am attempting to quantify the value that my customers would place on
receiving a Ground Shipped order within 2 business days of placing the
order for a niche retail product (wine glasses, corkscrews, etc.),
even when they don't need it in 2 days.  I am considering distributed
warehousing of my products so that 95% of the continental U.S.
population, using UPS ground, is within 2 days of a warehouse.

I need, however, some evidence that customer will value this
timeliness enough to generate sufficient repeat business to make up
for the increased operational costs and inventory investments.

I have read several surveys that state that timely delivery is
important (e.g., 90% of Internet customers value on-time delivery) but
nothing with anything that could be quantified or analyzed.