And, better flowers will result next year. The answer is no. Although some lilacs bloom better every year if flower heads are removed, generally it doesn't matter. Mock orange and rhododendron are other plants on which seed heads may be left. I prefer not to stake flowers so look for shorter varieties.
Peonies are one perennial that is usually staked.
Finally, spend a few minutes each day inspecting ornamentals for insect pests and disease, which are best controlled when spotted early. Check with your local garden store for organic or biological controls. If you are considering insecticides, remember that these chemicals also may harm beneficial insects. However, should you choose to use them, read the label carefully and apply at the rate indicated on the container.