I watch Scotty Kilmer's video's on youtube a lot, and follow his advice on this - drain and change your oil and filter once a year even if driving very little, and every 5000 miles - engines are very expensive, and oil is cheap. Your oil should be recycled anyway, so it is not very wasteful. Some fluids like transmissions are supposed to be "lifetime" and they are not easy to check, no dipsticks often anymore. So the "lifetime" of the transmission is when the transmission runs low on fluid, or breaks down quicker from oil transmission oil. On these, make sure the transmission fluid is checked often though it is more difficult to check now. And change it anyway until it gets higher mileage, over 100,000 - On motor oil, even if the oil were not to wear out, which it does - it picks up dirt and contaminants that circulate through the engine, wearing it - so get rid of dirty oil as he recommends, use good quality oil and filters -