Mesa uses Illinois caps for their 220uf's and Sprague for the 30uf's.There is nothing "magical" about them.They are better than your run of the mill jap caps,but many amp companies use the same.Yes,caps can last for 20 or more years,but I have seen them fail much sooner.Years ago a supplier in Manhattan who is long gone,showed me a tech bulletin from Sprague which recomended they not be used beyond a 10 year shelf life,and yes I am aware that shelf life and useage life are very different,but why take the chance?When caps fail it is true they will blow the fuse,but a catastrophic (explode) failure and the fuse blowing will happen simultaneously.Once they get old,they dont always exhibit any symptoms,they just explode.When they explode they can take other components with them,not to mention the almost imposible mess they can make,and if not properly cleaned the electro can become caustic,if they get leaky they cause your PT stress due to drawing excessive current,a slow death for a PT.When caps are installed they should be "formed"or brought up to voltage slowly,if it isnt done the caps life could be shortened,if you didnt install them your self,you dont know if it was even done.I have experienced every type of cap failure,from the simple "ghosting" to the exploded mess.I would not take the chance with old caps,they dont last forever.I have heard from many people that Mesa tells them "dont worry about them",from my experiences,this is bad advice,I am not saying you should stay up nights worrying,but why wait for a problem,anybody with moderate soldering skills and can find their way around an amp chassis without getting fried can do it,and as I have said in other posts,I have never changed caps that were around 10 years old and not noticed an improvement in the amps response,the losses are gradual and you dont always notice any deterioration until it is severe,but you will notice the improvement.When I do a cap change for someone who is skeptical I always give the guarantee that if the owner isnt happy with the improvement,I will put them back,no cost.I have yet to have to put any caps back.And it is just good insurance against problems later on.There are different opinions and experiences on this subject,so it is up to the amps owner as to what he does,but you cant go wrong taking steps to prevent problems,just like changing tubes before they blow and take other components with them.