Maybe forever, if you rely on an overly liberal interpretation of the maintenance schedules set by some vehicle manufacturers. That doesn't mean you should ignore them or even accept the manufacturer's recommendations, though; instead, add them to your list of items that should be checked annually after the first three or so years of ownership.
With accessory drive belts, most manufacturers recommend only a periodic inspection for cracks, fraying or other visible wear, and on some GM vehicles the first inspection isn't until 10 years or 150,000 miles, when someone else might own the vehicle.
Hoses? What about them? Most owner's manuals don't even mention radiator or coolant hoses (except that they can get really hot on an overheated engine). Other hoses, such as for the power steering or air conditioner, usually are mentioned only as something that should be checked as part of routine maintenance or when leaks are suspected.
Coolant hoses typically last several years, though anything longer than 10 years may be pushing the limits. Rubber weakens with age and from repeated exposure to hot coolant, so the older they get the higher chance they'll leak and cause the engine to overheat.
Drive belts are usually the serpentine type that snake their way around pulleys to power the alternator, air conditioning compressor, power steering pump and perhaps the water pump, and they're designed to last several years.
When to replace a drive belt is a judgment call by a repair technician, and it's up to the vehicle owner to decide if the time is right given the manufacturers have largely chosen to stay out of it. We would err on the side of caution, because when a drive belt breaks your car comes to a halt. Depending on where this happens and when, a belt that fits your car may not be available until tomorrow, leaving you stranded.
Don't confuse a drive belt with a timing belt, which connects the crankshaft to the camshafts and controls the timing of when valves open and close. Timing belts are out of view behind a timing cover and more complicated and expensive to replace, mainly because of the additional labor. Many vehicles have timing chains that are considered good for the life of the vehicle, but timing belts usually have a recommended mileage before changing. In some cases, that's as soon as 60,000 miles but in others it can be 100,000 or more.
