Re-blooming Daylilies? The best Daylily I know is Stella d'Oro. It'll bloom continuously IF YOU REMOVE THE OLD FLOWERS before they go to seed. All plants want to reproduce themselves, especially annuals. Take the flowers off, the sooner the better and all the energy going into those flowers goes back to the plant making it bigger, more vigorous and producing even more flowers. This has to be done daily as daylily means just that, a flower blooms for just one day. If you don't take the flowers off each day the plant is into making seed. Once they've made seed they relax. They've done their job.
From what I've seen, lilacs do well (flowering profusely the next year) if you cut the flowers off, prune out old wood (careful with pruning too much), fertilize lightly with lower nitrogen and make sure the pH is closer to 7 (more alkaline). They like the pH of a lawn and more often than not they are in close proximity to a lawn which gets fertilized with high nitrogen. Thus few blooms. The reblooming lilacs I've seen do set out new buds and do pretty well if you've cut the other flowers off. I've seen them bloom all summer through late summer, but not profusely.
Personally, I am a foliage person. Flowers are like the cherry on a sundae. Thrilling each and every one! But if the foliage isn't healthy there is no background on which to display the flowers. Lots of flowers, to me, mean lots more work. Lush foliage can be better than flowers...