I have had the same issue with texture thrashing for months now and putting down to the sim but now i know what it is.
I dont get the problem with either Singularity or the standard SL viewer. I did a clean install and cleared all the settings and cache.
I have a GTX780 working with a 6 core i7, 32gb ram and SSD's for program and storage on Win 10 and with all the latest drivers.
One thing i did noitce is that when the thrashing started firestorm became slow affecting everything even typing in the chat boxes, this was cured by celaring the settings and all seemed good for maybe 10 mins then the thrashing started again.
I run in Ultra and high and even down to mid but it makes no difference. Tried increasing the vram limit to 1024, the slider moves but wont stick after you OK it.
Tried other things that ppl suggest but nothing works and after the clean setup and that it does not affect other viewers i can only conclude that there is a problem with firestorm and some setups but just what i havnt a clue.