Can anyone tell me if really terminations can effect sound quality a lot?
As long as the contact resitance is low then no...not at audio frequencies.
Of course, a but a bad contact can be a problem. A loose wire or a loose pin in a socket can also be a problem. Occasionally a solder joint will work loose...a cold solder joint is expecially prone to this.
Compressing wires in a binding post should not normally be a problem unless the wires are physically cut (and it can work loose).
Proper termination will help prevent Oxidation. Oxidation will be very climate dependent... if you live close to the sea or on a houseboat then you can expect more oxidation problems. Proper termination of the wires with solder can obviously help reduce oxidation by preventing mositure entering under the cable jacket at the junction.