“Years ago Dave Chenault wrote about sending his Houdini back to Patagonia and asking them to replace the #3 plastic zipper with a #5 metal zipper and they did it.”
Sure, they did it for David Chenault. For me? Who knows?
I HATE #3 zippers on tent flys. #5 all the way. Moreover, for shells in particular, I tend to prefer anoraks over zip style precisely because the consequences of zipper failure is greatly reduced. And Anorak zips tend to be easier to manipulate with cold fingers.
I only use my ancient Houdini at home on day hikes, and haven’t had a zipper issue at all. the darn things 20 years old at least. Zipping up when my fingers are warm makes a difference, I guess, because I have major issues with zippers out on the trail. I’d much prefer #5 zips on ALL my jackets etc. I love the easy, smooth feeling of zipping up a #5, as opposed to the fumbling, bumbling around of a #3. And the constant snagging of inner materials in the zipper that keeps it from zipping, usually at the worst possible moment. I’ll take the one or two ounce penalty, gladly!