my opinion is that most buses have not had the fuel lines changed in decades.
 

every other year seems a bit caustios, though.     i usually end up pulled
the motor when i get a bus,   assuming the oil seals are bad,   and change
the oil seals, trans boots, and fuel line.

then again,  only my first bus was one that was actually being driven when i
got it.

and come to think of it, i dont remember if i ever changed the rear line on
the bug (oh, what shame!), which ive had for 5 years.  i did replace the
front bit, which was puddling a few months ago.

did i mention the 65 camper's fuel line made a big puddle on the floor when i
was getting it started, so i ran a line out of a 5 gallon can in the back of
the bus?   The 70 camper i got from  my dads neighbor had so much gook in the
tank from sitting for ?10? years, the lines were filled with black tar 

lines need clamps were they are under pressure -  at the fuel pump, and the
connections between fuel pump and carb.   elsewhere i dont think it's
neccessary, but go ahead if it gives you piece of mind.