if you have unread items going back for more than a year, chances are you are adding more to the list than you are removing. I guess hes right, i have observed this in myself and many colleagues from the days of delicious onwards. You bookmark/tag alot of interesting stuff because you are absolutely sure you will need it again and then forgetting about it after several weeks/months never looking at it again.
In the case that you need that knowledge again, you just dig it up on google (if you can remember it).
Might not be true for you, but i am sure its pretty common behaviour. I have given up on read-later apps because stuff just kept piling up. Noawadays i just leave the tabs open until i have read something of interest and if i figure that it isnt interesting enough after a few days i just close the tab and forget about it. That way i am managing my to-read list on a daily basis and it doesnt go back later than a week. With chrome sync its also easy to grab the open tabs on my other devices and read them there.
That being said things might be different if i had a long communte or had more freetime after work, but in that case i am usually reading a book, if i am reading anything at all. Giving the brain some relaxation time from the constant bombardment of tech "news" is nice as well.