Ink life with Epson 3880

I would like to get a larger format printer like the Epson 3880. I print bignoften enough that the cost is justified - UNLESS - the ink goes bad after 6 months and needs to be replaced before I use it up. I read somewhere that Epson says ink is only good for 6 months. I will print regular, but do not know if I will use all of each tank in 6 months. I am sure there are others in this situation. Based on your practical experience, what is the actuall useful life of the ink. I bet it is significantly longer than 6 months.

thanks.