I'm so happy to hear it was root hardy in 8a! If I see some, I'm buying it. I saw some in St. Augustine and really fell in love. And any time my eyes love a plant that hummingbirds also do, it needs to be in my yard.
I haven't overwintered this particular plant, but have many others & the routine is always the same for sun-loving plants, provide the most possible light water when the pot feels lighter. Trim if needed, to fit in available space. Almost always works for plants that are just perennials out of range, and when starting in the spring with an older, larger specimen, the results the following summer can be truly amazing.
For plants that have established themselves as root-hardy (or if not root hardy, and digging/pulling existing roots sounds undesirable,) taking cuttings to bring inside before the first frost can be a great way to have the best of both worlds, and more plants. I do that with Tradescantias, Datura, Hypoestes (polka dot plant,) and the past couple winters, cane/angel wing Begonia roots have survived where I chose to cut the plant instead of pull the whole things with roots to save for winter. I've never brought up Coleus roots to save over winter, just cuttings.
not impressed! After 2 years let it go. Here it died to ground in winter, but would come back. I am zone 8a. Just thought it was a waste of water in the summer. 
Russelia equisetiformis by longk48, on Flickr
