It really depends on how well you take care of your amp, to justify tube life, but I've been advised that 6 months of playing just about everyday at average levels would dirty up the tubes a bit and possibly bring about a need for new ones. I wouldn't put your money on the tubes being the problem yet though. I would also say take it to a shop. Get it done, bam... few bucks later, working amp, and no worries about its problems, only yours. Your guitar skills that is. Its no fun when the gear won't hold up. :(