I had this issue since Sept or so.... I enabled the 3GB switch in Windows (google "enable 3gb switch" for instructions) and have not crashed since. I am using 32-bit Windows 7 with 4GB of RAM.
The swtor process still grows over time, so it will crash eventually... but crashing every 8-9 hours is much more tolerable than every 90 minutes.
Thank you very very much.