bridge cache

hi,

i've got some large external drives full of images, mainly pdf's..

when generating bridge thumbnails for them, i only used the "export cache to folders" option.

working with bridge as a graphic designer using a ssd system drive pc environment, brings me again and again to the point

when bridge messes up all my system space in the "roaming" folder. (even with "export cache to folders" option).

so i concluded this might be because of the rather larger preview files, so i cleared up the "1024" folder in "roaming"

but it didn't help much. i noticed the "256" folder was huge too, so i had to purge it. BUT! oh my god! all my thumbnails,

from all the drives, all gone!

does the "export cache to folders" option work, or how to make it work?

i wish i could create and locate my thumb databases individually .. to the drives where the images are, and being able to load..

(as thumbsplus could do 20 yeas ago...)

regenerating all these thumbs again and again for external backup drives consumes a lot of my work-time, ..is there another solution, pc system independent?

thank you!

ps. this is one of these files, code generated vector--quite large and mostly quite many to handle..
http://ptgmedia.pearsoncmg.com/images/9780133927054/samplepages/9780133927054.pdf
and--btw--a job i did for adobe!