Plenty of electronic components will drift over time. You probably won't hear it s it is gradual. In direct comparison if you had a time capsule and kept a new one 20 years later to compare, you may be able to hear the difference. Not all R2R boards are the same so a general statement is that it won't be a factor. Is your salesman saying that a chip set won't also degrade or drift over time? Well at least you will be enjoying your music more until that time comes!
Happy Listening.
Happy Listening.