Sony WEGA.. quiery on picture tube?

I have a 21 inch Sony Wega flat tv since 11 years, I do want to go in for a slightly bigger LED Sony, but I am unable to decide since the CRT tv is still going strong. But of late, I have been seeing some signs of fading in the tv, i cannot describe what happens precisely, but to describe in the best way possible, whenever the screen has more white in it (during the ads with bright white background or any scene with white in majority) the bluish white suddenly becomes milky white, and then again bluish white after 3-4 seconds, sometimes longer. This happens in every other channel. Is the picture tube decaying? or is it something else? do u think i should replace it with an LED? or will this TV do the job for a few more months? People who have experienced this problem or people with technical know-how on CRT tv's please respond. Ur opinion will be valuable. Thanks