04 Quest SE squishy brakes

We purchased a used 2004 Quest SE about a year ago and have had an "issue" with the brakes since we got it. At times, the pedal reacts as one normally would expect, depress a bit and the brakes start working. Other times it feels like you have to push the peddle to the floor to get the thing to stop. Letting off of the peddle and then reapplying then gives the correct feel.
I replaced the back brake pad and had the rotors turned down and that appeared to help at first. But now it is acting up again. Had it in the dealership for service a couple of weeks back and they said the front brakes needed work. Didn't know whether to believe them or not as I am skeptical of dealerships and their "suggestions". I have yet to pull the front wheels off and take a look at them myself.
Anybody else have this issue or does anyone have any suggestions? TIA.

Sounds sort of like a
Sounds sort of like a partially failing master cylinder. Could be a sticking ABS module or bad hose as well. If it is something intermittent, it is not likely to be rotors or pads, unless the intermittentness (sic) is associated with high temperatures (brake fade).
Squishy brakes
I think you should first take the wheels off and do a visual yourself to see the conditions of the rotors and pads. If they look good, then I think you should first try bleeding all 4 brakes in case there is air or moisture in the brake line.
2004 Nissan Quest SL