I've had a Regza 52XF550 for about 4 months now and so far (knock on wood) it is nearly flawless. Just keep in mind that all manufacturers occasionally have issues and electronics of all kinds occassionally go bad prematurely...but in general, if it survives the first ninety days there is a good chance that it will last a very long time.
If you want 'peace of mind' (read 'enriching the insurance company') you can buy an extended warranty but the insurers have far more data than any of us on the expected longevity and percentage failure rate and they are not in the business of paying out claims; they are in the business of collecting premiums. If you apply for life insurance after having 3 heart attacks in 2 years you will be denied; likewise, if a Toshiba Regza or any other brand/model has a very high premature failure rate you would not be able to buy an extended warranty on it at any price.