All the hoses hooked to your carburetors, the vacuum ones and the drain ones,
can become rotted and cracked.
The vacuum ones can make a difference in how your bike runs.
The O-rings under the intake runners need to be changed when you
start seeing "tobacco" stains around them. Getting your hand back
in there to change out the carb drain and vacuum hoses sure is
easier when you've got one (or some) of the intake runners off

The bigger gas lines on my 97 are probably original. They still seem good
when I take the tank off. I guess they're made more robustly, since a
failure similar to my rotted vacuum lines would probably result in
a ball of flame...
-Mike