If it is the smaller, Japanese Spirea (w/pink/purple flowers) ...

Though it is basically a once-per-year bloomer, ... prune off the faded blooms ... and it may bloom some more before the end of the season.

Nah, it won't bloom again. Thanks for the thought! I was just hoping there was some magic I could perform to make it bloom longer than just under two weeks! It has white flowers and stands about 7 feet high.

One possibility is to selectively prune back about a third of the stems/branches, about 6-18", in the mid-spring, as you see new growth. This should cause delayed flowering on those stems, and extend the season for you. If you REALLY wanted, you could do the same on another third a few weeks later, but that may be overkill. And this will work only if the spirea flowers on new growth. If it flowers on old growth, it won't work.

It blooms on last year's growth--that's why I figured it wouldn't bloom again, but I did some googling and apparently it just might--so I deadheaded a few branches today to see if it "works."

There are so many--and so much old wood, I was at it for about 1/2 hour--and there's still lots of old blooms still on the thing.

Still, I could almost get into a zen like state with the process.....