Yes.

I do find they are as tough as old boots and if I need to prune, to tidy they border, I do and they still multiply!

the more foliage left on the more chance of good flowers next year. the flower is being formed from now onwards really.

I have just pruned my 'Lucifer' variety back to half way,mainly so I can get to the back of the border,as they are very tall,and floppy now....I do it every year,with no detriment to next years flowers..plus lots of new ones are forming as well.
My shorter varieties,are left to die off naturally,and the brown foliage pulls away easily in spring..