the direct cause of fade is down to your fluid and pads, get some good pads - ferodo ds performnace are a good option aswell as the mintex 1144 compound pads (used by the police t5's). then get some dot 5.1 fluid and change it regulary.
bigger discs will help with fade as they run cooler, another plus is they are les likely to warp.
i found the brakes on my 480 to be some of the best i have ever used, never took them to fade so cant coment on that.
the best setup will be to get as big as poss discs (vented), good pads and good brake fluid and you will be sorted.
Brakepads, discs, handbrake. The brakes are crucial for your Volvo 480. Use this category to learn all you need to know!