I have not replaced any cooling lines or hoses on mine yet. Did replace the water pump last summer as the seal got leaky. But all my hoses seem to be in excellent condition still. Its remarkable for a 12year old vehicle especially as frequently as its driven. Ive considered flushing the radiator and transmission cooler this summer but it stays as cool as when we bought it in 02. The best maintenance on these trucks is driving them. Keeping the seals and rubber all in good form. If i ever let it sit for a few months i feel it would deteriorate but it has been driven nearly every day for 12 years straight.