Hello, Shelli. You can deadhead the flowers if you wish. Some people prefer to leave them there for winter interest but eventually, they will "fall" on their own. Hydrangeas do not require regular pruning but you CAN prune if you need to. They develop flower buds on new wood so pruning is best done before they bloom at the start of summer. So you can prune after flowering for example, nor now in the Fall, or during Winter, or in Spring. I would start to hesitate doing any pruning in mid-Spring.

I usually prune off all H. paniculata blooms before winter sets in. In the past wet snow and/or ice accumulated on the blooms and broke the stems - I prefer doing my own stem pruning in the very early spring.
Marshall

I've had the experience of Ma Nature doing the pruning ... I don't think she is quite adept at it!!!

My Kyushu tree & Little Lamb are in the line of fire when The Alberta Clipper (we fondly call our Winter blizzards/windstorms) passes through her favored corridor!!! So I'll clip many & leave a few to gambol a bit for Winter interests sake!!! I lost a huge center cane from my Kyushu tree last year ... got 3 good plants that flowered this Summer (gave 2 away)!

BTW Marshall - have you posted photo of your 25 LLs you planted around the Flag pole of your Library? I've been wishing to see how the turned out?

Please do if you haven't, it would be a treat to see - & if you have I'll search for it!
TIA