The beauty of EI type dosing is that you don't have to 'micro' (pun intended) manage your tank.
Your putting enough in to make sure you don't run short. There is a very wide range for dosing without harmful effects. You would have to go bat crazy to test the limits. In 10 years of EI dosing with substrates ranging from Pool Filter Sand to Eco Complete to Aquasoil I've never had a problem with dosing too much and I usually dose toward the high end of the recommended ranges just to be sure you don't run out.
Although there is K in the KNO3 I still dose the SO4 just to make sure it doesn't run out. Some extra K never hurt anyone.
Water changes are important. Just do them. It's good for the fish and it's good for the tank especially if you have good light. Any organics left in the tank will develop into algae problems that much quicker with good light. You could get away with less in dimmer tanks, but as long as your dosing the water changes benefit all tanks.
I haven't tested my tanks water in over 5 years. If I have fish I just make sure the co2 isn't too much. The EI dosing is very compatible with most lifestyles if you don't want to waste your time checking every parameter. If you enjoy that stuff, then go right ahead, but it isn't necessary. IMO of course.