The most vulnerable components as far as lifetime is concerned are **electrolytic capacitors**. Standard lifetime is 2000 hours, long-life parts are usually 5000 hours. That's not much, but there' a rule-of-thumb which says that for every 10°C you stay below specified you can double lifetime. So a 105°C cap working at 55°C will have a lifetime of 2000 * 32 = 64000 hours. That's 7.4 years of **continuous operation**.  
Here we touched an important factor: **temperature**. High temperatures decrease components' lifetime. If you want to go from 24V to 3.3V at 1A in a **linear regulator** you'll have to dissipate 20W. That's a lot. A **switching regulator** may be a better solution.  
  
Concerning special protection components I would use a **fuse** to protect the product as a whole, and a **varistor** on the power supply input to protect against spikes specifically.