Winter starts here in two days where I live at Tolga at 757 meters altitude near Cairns.
With my thrip invested Sarracenia, do you think it would be a good idea to cut ALL the leaves and pitchers of them including the older green growth now as the plants are mainly dormant. I would leave the younger shoots that are not infested if there are any. I am just wondering if cutting off all the older green growth as well could set the plant back in the coming growing season because I heard that the plant should have some green growth left on as a nutrient source for the plant. However, removing all the older green growth would get rid of more of the thrips which are probably on this green growth. It is also much quicker to remove all the leaves than only selecting the dead leaves.
I regularly clean off all above ground growth on my Sarracenia in the middle to end of winter, it should not set them back. This is excepting Sarracenia Purpurea and some of its Hybrids. this will not rid you of the pest problem as they will be in greater numbers in different form in your soil, so your idea to follow up with Spinosad is also a good one.
All that is gold does not glitter not all those who wander, are lost. Tolkien.
You may have to try a couple different pesticides be them organic or not. Thrips seem to build resistance easily, so what works for one person may not for another. Here in the Pacific Northwest of the US they are immune to imidacloprid, but Acephate works well. Spinosad would be great to try. Also worth a try is a Beauveria bassiana product such as Botaniguard which is good for sucking insects.