Toyota Repair: Toyota Celica ISC Valve Problem, toyota celica, toyota dealership

Question
I have a 98 Toyota Celica GT Manual Hatchback that I bought new.  About every 12,000 miles my Celica starts to have problems with cold starts.  I took it to the Toyota dealership and they replaced the ISC valve and cleaned the throttle body.  This fixed the problem until about a year later when the same problem occurred.  I took it back to Toyota and again they replaced the ISC valve.  My celica once again worked great until about a year later.  This has been happening since I bought the car, and I now have 74,000 miles on it.  I've had the ISC valve replaced 5 times now (under warranty), but once again the celica is starting to have cold start problems (no longer under warranty).  

Toyota has never been able to give me an answer as to why the ISC valve keeps failing.  I know this is somewhat of a problem on Camrys, but I've never read about this happening to Celicas.  I live in San Jose, CA where the weather is mild and there isn't a lot of pollution.  The most frustrating part is just not knowing what is causing the problem.  Any ideas or theories would be greatly appreciated.

Thank you.

Answer
The Celica uses the same engine as the Camry, I have no idea either why the problem happens on a yearly basis, what happens normally is that the valve starts sticking mostly due to crankcase fumes which enter the intake system through the breather hose from the valve cover after time the valve gets carbon builtup and it will hang up, try to have it cleaned along with the throttle body, this may help and it's a lot cheaper than replacing it.