Ever since I was diagnosed in 1995 my CD4 count has hovered around the 200 mark - just above or below. It reached a nadir of 40 and then I started combo therapy in 2005 - since then, it has hovered just above 200. Recently, however, I was astonished to find it had peaked at 350, the highest it's ever been in 15 years. I see on this site that people should start treatment if their CD4 is 500 or below. Mine seems to be naturally low. I have never had a day's illness in all these years. Should I be worried that I have only ever attained 350 in ten years?

You are likely one of those people who has a "slow-low" CD4 count response after starting HIV treatment. That is, the lower your CD4 count is when you start treatment, the slower your counts are to respond and the lower the overall increase is over time. Some people never get over 200 despite years of HIV treatment. Whereas some will continue to increase very slowly like you. It is unlikely that you will get to 500, but the good news now is that your immune system has sufficiently recovered that you are unlikely to develop any serious infections associated with HIV infection.