Kingston DT Elite...slows down

When I install a fresh copy of the portable apps on my DT Elite they all work responsively.

After a time the apps slow down. FF for example is crawling. So I reinstalled FF and it is a bit better but still slow. I used to run Faster Fox, Scrapbook etc but with the new install I omitted these extensions and it is still slow.

I did not change any of the settings so 0MB cache etc.

Does anyone know why this happens. I have also reformatted the DT and that helps but soon enough FF slows down. This does not seem to happen so obviously to Thunderbird for example.

Am I expecting too much from the DT? Have the write cycles caught up with me?

I would appreciate your help. Portable Apps have changed my computing life but I need a reliable and speedy drive.

Thank you all.