They will probably keep going for a few years, if you have several why not trim one or two back a bit further and see if it rejuvenates it. Otherwise why not save a bit of seed and grow your own, then they will be reincarnations of the ones that your husband set. Make sure they are firmly bedded in when the winter winds rock them about.
Other advice will be forthcoming I am sure.

HI Patsy, Welcome to Goy! you must be so attached to those lovely plants! I have discovered that perennial wallflowers are some of the easiest plants to propagate from soft cuttings. Find some newish growth without flowers and cut it off (3" or less will be fine) with a sharp knife or good scissors, strip off the lower leaves and pop it straight in to some multi-purpose compost around the outside of a clay pot if possible. keep it moist but not drowned, in a sheltered spot, and you should soon have new rooted cuttings. They are lovely, but sadly they tend to get really leggy after a couple of years, so I tend to just replace them with new ones from cuttings. I grow them on for a year in pots before planting them in the soil...it may take a lot less time depending where you live as I am in the North East in Scotland :) Hope this helps!