Does WPW syndrome affect life expectancy?

Depends. If diagnosed and properly treated (usually with a procedure called an ablation) one can have a normal life expectancy. However, prior to treatment a patient may have a fast heart rhythm that can be dangerous and potentially life threatening.
NO. It doesn't have to. There is a rare instance in which someone with WPW also develops atrial fibrillation. The combination is deadly. But WPW is curable. Once it's identified, it can be ablated if there are symptoms. Many people with WPW have no symptoms and don't need anything done.