Can you re-use those anti-static softener dryer sheets more than once, or are their magical abilities depleted after a single load?

I use more than once.

I have tried this, and no, not really. However, even in Colorado, which is Static Central, I got easily the same affect from using half a sheet.

I use half a sheet. They easily tear in half if you rip in the right direction.

Get those dryer tennis balls.
Save yourself a pile of money, and there are no chemicals or scents.

I don’t use them because I don’t believe in magic. I hang my clothes out the old fashioned way (even in winter). No static when you use the air and the sun.

A used dryer sheet makes a good dust cloth.