Short Answer: No
Long answer: There are many reasons not to replace fillings that are intact and functioning properly. For starters, there is some risk to every dental procedure. Every time a filling is removed, there is a risk the tooth will fracture, will become sensitive or have other long-term issues. Secondly, metal fillings have been time-tested and proven to be reliable extremely long-lasting solutions to cavities. Placing white fillings is a very technique sensitive procedure which, if done incorrectly, can show signs of failure after just a few months. In other words, if a white filling is not placed with a high level of skill, you might find yourself needing to replace it five times in the time you would have replaced one metal filling. Finally, why should you or your insurance bear the expense of this procedure if there is no clinical reason for it? This would be like paying to upgrade your computer’s software only to get a new version with a nicer interface but which is not necessarily better and could even be worse than the older version!
As I see it, there are only a few reasons to replace metal fillings. One might be for cosmetic reasons, as white fillings look more natural than the metal ones. Although I discourage patients from replacing their metal fillings for this reason and I always discuss the risks of doing so, it is a matter of personal choice. Also, some patients are concerned with mercury vapor and mercury products emanating from their metal fillings. This is a very contentious issue among dentists and the public. Some dentists believe mercury fillings are bad and others think they are perfectly safe. Some in the public have claimed that moments after they had their metal fillings removed, they were cured of chronic illnesses like asthma and multiple sclerosis. I always find those claims peculiar because what is known is there is an elevated concentration of mercury vapor emanating from metal fillings during the process of removing them. Most people have elevated mercury levels in their blood after having these fillings removed. So if one were cured of multiple sclerosis moments after having their metal fillings removed, then perhaps mercury vapor should be studied as a cure! Or perhaps what is much more likely is that there is a strong psychological component to the process and this cannot be underestimated.
In all fairness, we need to give the other side of the coin a fair shake. Although the position of the American Dental Association is that mercury fillings are safe, it is impossible to prove such a statement. After all, it is not possible to prove a negative. Mercury is a known toxin and it would be prudent to minimize exposure to it. As such, I have chosen not use mercury based filling materials in my office. But this is a far cry from actually recommending someone replace their metal fillings because of the mercury issue. In fact, the American Dental Association has taken the position that any dentist who does this is behaving unethically.
I believe in a more level-headed and logical approach: If there are sound reasons to replace a filling (it is cracked, there is new decay around it, etc), then replacing said filling with a non-mercury alternative minimizes exposure to any mercury. That seems to be a good compromise by my standards. But this is only reasonable if the white filling replacing it is done using the best techniques and with the utmost care (see discussion on proper technique in the introduction of this site).