I am an advocate of child-led weaning. Why is the child being weaned by 12 months? New guidelines are moving toward 24 month minimum for a breastfeeding baby.
All babies will eventually wean themselves if given a chance. If your child is very-much in love with the boobie, I suggest continuing to nurse him. Breastfeeding is such an intimate, soothing, calming, protective, nourishing time in our lives and that of our children. Force weaning a child who is not ready can be traumatic for them.
Don't wean because you think you have to - most of the world breastfeeds their babies far beyond 12 months. The actually weaning age of a human child is between 2 and 7 YEARS of age. Some babies do wean easily, and perhaps your son is one of them. But if he is nursing 5 times a day, I would be very surprised if he is going to give up the tatas easily. Breastmilk beyond 12 months still offers an amazing array of protection and nourishment for a child.
My son is 22 months and quite the boob man (my daughter weaned at 3.5 years). I recently had Shingles and he had not had the chicken pox vaccine. When I called my pediatrician, she asked if I was still nursing him and I said yes. She said he most likely won't come down with chicken pox because I am giving him antibodies through my milk. She said, "It is great that you are still nursing - it protects him from the world in ways you couldn't imagine." And nope - no pox for him :)
You can also continue to breastfeed safely while pregnant (though some babies WILL wean when you are pregnant because the milk changes taste and consistency). I know many moms who tandem nurse toddlers and newborns happily.
:)