I have seen well maintained machines run for over 12 years. I generally see solvent printers lasting about 6 - 8 years before being junked. If I owned a shop, I would probably replace my equipment every 5 years. The main concern is what maintenance is costing compared to the cost of a new printer. Printer prices are constantly going down due to higher competition in the past decade and maintenance parts prices are going up. If the cost to repair your machine starts getting towards 40-50% of the cost of a new printer, it's hard not to just bite the bullet and buy the new machine. If it were me, I would buy a machine on a 3 year loan, run it for 5, trade it in for the new model and repeat until I can buy the printer in cash and run the old printer into the ground.