The owner's manual for my 2004 VStar Custom says that the brake hoses should be replaced every four years.  Does anyone have any opinions, comments, or experience here?  

I just sold my 98 Virago 1100 and to my knowledge the brake hoses were never replaced. You should check them though. If they look like cracks are forming on the outside (like an old tire gets), you should replace them.
That being said, you should replace the brake fluid. While you have the brake fluid drained, you should take the hoses off and check the inside of the hoses. Take a q-tip and rub around the inside, if it comes out really black and kinda snotty looking you should replace the hoses.  

One quick test, and it won't work for HD owners (they use DOT 5 fluid). You have the little view sights for fluid level. They also let you see the condition of the fluid. When the fluid is new, it's almost blond. If it looks about the color of caramel, it's time to change it.
One of the reasons it doesn't work as a test for HD is water doesn't get absorbed into the fluid, and it's heavier than the fluid, so, water can build up at the brakes