As mentioned, you only have to replace your rotors if they are worn down beyond minimum specs or you have a warped rotor causing a pulsing in the brake pedal. The PO of my car had cross drilled on back and rotors that were cross drilled
and slotted on front. The problem I had was that the front-left rotor was slotted only on the inside (must have been made on a Monday). I was having brake pedal pulsing along with a steering wheel vibration so I replaced the fronts with cross drilled only to be consistent with the back rotors. IMHO, in most applications and for most people, cross drilling is unwarranted overkill. But it does look cool.
I get occasional squeals but the brakes are very smooth now as they should be. Brake pad material choices can make a big difference in brake noise - the more aggressive the pad, usually the more squealing you get so that would be my next recommendation if you can't live with the noise you have now.