Whether you are a serious biker or not, you may be a bit anal on the quality of your bike’s components. That is perfectly fine as there is nothing wrong with wanting things up-to-date. So, you may be worried about how frequently the bicycle handlebars should be replaced. But, you should just take a breath and relax as these babies are designed for the long haul. That is if you use them correctly and they do not get damaged.
It seems like a brainless answer but you should only replace them if you have crashed and they are damaged beyond repair, simple. No matter if they are made of carbon or aluminum, there is really no reason to periodically change them unless you feel they do not perform as you desire anymore.