You can recycle trees where where limbs are tired, but the trunk is still in good condition.
A lemon tree can become an orange tree or even a mandarin tree. As long it belongs to the category citrus. Looking for a new tree, let e.g. the citrus tree grow until next year without cutting it. When ripe, cut the tops and plant them in the trunk of a severed citrus tree. Attach the limbs as the picture below and let be.