Just my opinion, and I'm originally from Vancouver, BC also nominally zone 8. I don't think brugmansia are going to survive your winters in Oregon even if it doesn't frost or snow. You have weeks of short, grey, wet days in winter and the nights will go down into the 40's or 30's nearly every night.
Zone 8 in Florida is much MUCH different than it is in Oregon, that's all I'm saying. Down here we have to protect our brugs on the odd night or two that plunges into the 40's or 30's during winter, but we get longer, sunny days in the 70's and 80's here as well - I call it "Pacific Northwest summer" weather that we have almost all winter except for the occasional cold front that makes it this far south. So my brugs grow and bloom all winter here as long as I remember to mulch and protect them.
My mother grew brugs in Vancouver, but she brought them indoors for the winter. Thankfully she had a "sunny" southeast facing window where they were able to at least keep growing through the dark, damp winters.
I'd advise you to plan to keep it in a large pot, and move it indoors for the winter if you have a sunny window for it to live in front of. If you do this then, yes, for sure you can plant a new brug any time.
