Get out and pick your holly for Christmas decorations now. As the berries ripen the birds descend and scoff the lot just when you are not looking.
You can condition the stems, leaves and berries and placing stalks in a glycerin solution. They will take up the liquid and become supple and longer lasting. Crush the stems and use warm glycerin then leave for a couple of weeks.

These variegated Holly trees are part of a holly hedge grown for decorative purposes not cutting for Christmas.

These berries look like they have already had the glycerin treatment but this is just how they were growing in a local Yorkshire field.
I dis leave the berries for the birds in case it is a cold winter.