As with most things, the older they are the more likely something is going to go wrong at some point. My main concern would be the support from Veritas. Providing you have them under support, then if anything does go wrong then you are covered anyway. The 5330 are end of support 30/08/23 (https://www.veritas.com/support/en_US/article.100045773 ), so i would be aiming to replace them by then, if not sooner. It all depends on your companies appetite for risk and if they require things under support etc.
My own rule of thump say when hardware reaches 5 years, there should be a plan for replacement of the hardware.
But there is a few other topics to consider the statement above: