I’m in Western Washington north of Seattle zone 8b. I’ve been at my house for 5 years and the vines are about 2" in diameter so I’d guess they were here for a long time before we got here. The previous owners were not much into gardening so I don’t think they paid much attention to it. I’ve never seen it anywhere else on my 5 acres but where the two are planted. I have had some long vines flop off of the trellis but I just pulled them up. We get very little summer heat so that might be part of it. Most summer days are 70’s here with maybe 10 days hitting 80 and we rarely hit 90. Maybe 1-2 days a year. I’ve also heard maypop passion vine can be a problem in other parts of the country but here it is hard to get it to grow much. There are a lot of “invasives” in other parts of the country that don’t invade here like Autumn Olive and butterfly bush. We also get less sunny days per year than most of the country. Our average is 152 vs the US average of 205 so less photosynthesis to go around 
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