Hello Bryan,
    One of the most comprehensive reports I rely on and often site was done
by the University of Vermont and US Army Cold Regions Research and
Engineering Laboratory published in 1996.  It is still relevant and has info
on BiGlass and other "modern" treatments.  I would suggest you contact the
Department of Civil and Environmental Engineering at UVM.  The report was
titled Testing the Energy Performance of Wood Windows in Cold Climates.
        I use the "Estimated Useful Lives of Depreciable Hospital Assets"
1988 (American Hospital Association) for durability. (It is accepted in
Connecticut by our gummint).   However I tell clients that vinyl or metal
windows need repairs and replacements in five to seven years and total
replacement in 15 to 20 and that restored historic windows need painting
every five to six years and have a sixty year life.  Of course all types of
windows last longer if you don't use them.  "Alarm will sound if this window
is opened.  If you need fresh air, call the sexton or go outside.  This is
an historic church;  What's wrong with sweat anyway?"
    As for my preferences:  reduce air infiltration, tune up and restore the
originals, and install interior storms if desired by users, but not til they
have experienced the windows restored for a full year. Maintain your
windows, set up a schedule and budget and stop those kids from chewing.
    Also, check with the National Preservation Trust on the reports for
Affordable Neighborhoods.  I worked on one for the Dwight Neighborhood in
New Haven in 1998, but there are reports for at least four other towns.
Lead was the most dominant safety issue.  I think all the Guidelines for
affordable neighborhoods include (not preferred, but allowed) vinyl windows
and have design guidelines as to their installation, proportion and
appearance.

Best,
Leland

PS  Can you post your reference list when you finish?