Fuses don't go bad, or age or anything like that, the only reason to replace them is if they blow. I can't think of any reason that I would replace them unless someone has replaced them with the wrong values.
The G-9000 has the following fuses. All fuses are "fast blow" 2AG
one 12A 250V
four 10A 250V
four 1A 250V
one 2.5A 250V