If you're happy with the DW, then keep it - a new one may actually be worse and less reliable. A DW is something that can easily be replaced later, if necessary.

Like you, I was urged to replace my DW when the kitchen was remodelled. I resisted - it was a 6 yr old Bosch, working perfectly. It's now 4 years later, and the thing still works like a charm. My theory was that dishwashers have standard dimensions, so it could be replaced as and when necessary without having to make any alterations in the kitchen, whereas an oven or fridge might be more difficult. I could see no reason to replace a perfectly functioning appliance, and clearly I made the right decision.