The good thing with Kaffir Limes is that you don't have to wait for them to fruit to use them. Many Thai and asian dishes call for finely sliced Kaffir Lime leaves. They are predominately used for their leaves and zest, as they do not have much juice, but the juice can be used again. They are easy to recognise because of their double leaves and are usually grafted onto some reliable rootstock. I was careful to pick the one with the strongest looking graft and lots of bunching branches rather than a straggly looking one.
When looking for a photo for this post (as I forgot to take one) I found out that they are useful in green cleaning as well...
"Kaffir lime shampoo leaves the hair squeaky clean and invigorates the scalp. It is believed to freshen one's mental outlook and ward off evil spirits. Kaffir lime has also been used for ages as a natural bleach to remove tough stains. When I was growing up, mother did the wash entirely by hand, and nothing worked better on stubborn stains than a few drops of kaffir lime juice, mixed with a sprinkling of detergent. Not only does it clean effectively, it is inexpensive, natural and sweet-smelling. For rural villagers, a single kaffir lime tree supplies enough limes to keep the whole house and family clean.
In folk medicine, the juice of kaffir lime is said to promote gum health and is recommended for use in brushing teeth and gums. The essential oils in the fruit are incorporated into various ointments, and the rind is an ingredient in medical tonics believed to be good for the blood. Like lemon grass and galanga, the rind is also known to have beneficial properties for the digestive system."
(From this website)