If you deadhead some plants you will be rewarded with longer flowering.
It is good to start deadheading some of your plants if you haven't started to do this already. Plants grow flowers as a way to reproduce themselves and so if you cut off the flowers before they can set seed then the plant has to start the process all over again. You benefit by prolonged flower colour in your garden or container.
As well as herbaceous perennials that benefit from deadheading, some shrubs such as Buddleia can continue flowering if deadheaded. Roses and the new Patio Clematis need deadheading as well. If you take off the flowers on the Patio Clematis you should see new flowers already forming behind just waiting to come into flower. Don't forget that watering and feeding can also help.
Some perennials benefit from the flowering stems being cut right down to the base after flowering such as Lobelias,
Achilleas, Leucanthemums and Penstemons as even if the plants do not produce a second flush of flowers they should start producing fresh growth around the base which will strengthen their chances of getting through the winter and clumping up for the following year.
Some herbaceous plants however throw out more flowers from sideshoots such as Polemonium 'Bressingham Purple' and Veronicastrums so chech first before you cut the whole stem down. With these varieties just cut the dead flowers off next to the next set of flowers or leaf axils.
Perennials such as Anthemis, Coreopsis, Cosmos, Rudbeckias benefit from regularly
deadheading the individual flowers until they start to look straggly and flowering slows down and then they can also be cut back to the base.