Ed: You can prune them off if you like but it won't have any effect on tree health. It might improve your health by not getting stabbed. My Washington navel has thorns. I've trimmed a few but mostly just try to avoid contact.

The Fruitnut

Trim them if you want to. It won't do any harm. Every time I move my lemon or Key lime into or out of the greenhouse it looks like I have wrestled with a barbed wire fence. I am always bleeding and they are extremely painful wounds.

Checked the thorns on my Washington Navel. They are only on the most vigorous shoots. None at all on the outer small wood. Even the largest and oldest, 1-2 inches and 3-5 yrs, are still green so they are still photosynthesizing. I'd still remove them just to make the tree better company. It won't affect the production or health of the tree whether removed or not.

The Fruitnut

If you're around it a lot, yes take them off.
It is easy if you break them when the branch is growing while the torns are soft and tender.

Prune off when green so they heal sooner. You will need to prune the thorns off ever year or every other year depending on your plants soil and light it receives.

Thorns are a built in defense against predators (you) from eating its fruit.