I sure wish my tank can go on for another 5 years. But there is a myth that DSB will eventually crash at about 5 year time.
Anyway, beside DSB, I also had a refugium, tons of LR (berlin system) and two skimmer to help in exporting nutrient. To tell the true I had not done water change for 5 years. hehe.....dont try this on your tank, it might not work for you.
I also planning to add on a small tank link to my current one, to serve as propagation tank and maintance tank ( water change in future ).