Capacitors will hold a charge almost indefinately, if they are of good quality and in good shape, unless they have something to let them leak down. I'm not up on how they are being used in today's car stereo systems, but back when I was working in an electronics company(20+ years ago) we would always put a hi-ohm resistor across the capacitors to let them leak down over time, something like a 1megohm or more . Not sure if that's the way it's done in car stereo systems now. Are the fuses slo-blo type so they will take a bit more of a spike before they blow? May need to have a way of leaking the capacitors down before putting in a new fuse.
Next, may want to pose this over in the Audio forum. They are a bit more up on how car stereo's are set up now. I'm still kinda old-school on this.
