I read 75% of HIV infected people taking meds will eventually learn they have to switch to different meds; the virus evolves and outsmarts their regimen. Is this accurate? Secondly, how will age factor in this? I'm 59, POZ less than 2 years, almost always have been undetectable and started with CD4 at 740, now over 1600. How much time might I have before my Isentress/Truvada stops working?

Not true at all.

Most medication switches in the US in the present are due to side effects. Resistance only occurs if a patient started a suboptimal regimen that did not provide at least two active medications to which their virus has not developed resistance, potential drug interactions that lower medication blood levels or if the patient is not adherent to medications. You seem to be doing well at keeping your virus suppressed, so I would not worry about this. There are several studies that have followed people over 5 years on certain combinations (Kaletra plus nukes, for instance) that show people still preserving an undetectable viral load after 5 years of taking the same combo.

Nelson