As soon as you don't bump solid objects with lens, no need to protect - generally. Except you use camera in harmful conditions, and then think about protective case, too. And safety suite for you, in case if conditions are really bad 🙂
UPD: best move would be getting lens shade. Original are expensive and I can't suggest which from current to get. But it gives protection to image, and some say - to lens too. It really depends on type of accident - you drop it on concrete lens down, or gull hits front element or camera swims in sea. Best one can do for camera - use it, then it at least doesn't gum.
Don't overdo with lens cleaning, that's all. This is how I managed to scratch some on my first cameras. If you clean lens, do it properly. I promised myself not to touch lens in field if it gets little dirty.