Even just changing the shift points, under an average "load"/throttle input, eco mode wants to get to the next gear pretty quickly. Too quickly most of the time i'd argue, keeping rpm way down and really lugging the engine. That's not good for it and can lead to excessive carbon buildup, especially if it's driven like that all the time. I used to keep mine in eco mode all the time, (I'm all about that MPG) but I now keep it in normal mode around town and country road driving. Eco only on highway/interstate now. I also give it the ol "Italian tune up" 2-3 times a tank of gas, especially right before a fill-up, getting those rpm way up there for a bit. Doing that increases pressure in the cylinder and puts some heat in there as well, all good for helping minimize carbon buildup on the piston and around the rings, which is super important for today's modern engines and especially GDI engines. Now if it only worked on the exhaust valves like that. Oh well.
