Getting the "right" amount of treatment for your injuries is a balancing act. You certainly don't want to get too little treatment or stop treatment before your injuries have resolved. On the other hand, it is not wise to "over treat" or get unecessary treatment. Insurance companies will try to punish you for over-treatment, which will make your case harder to resolve and could weaken your position.
How much is too much? I cannot give you a good rule of thumb. It depends on your injury. The best thing to do is pick a reputable doctor and follow their orders. That will always be easy to defend.
If your treatment is reasonable and necessary, your case will be easier to resolve and you will have more credibility with the insurance adjuster. If, however, the bills and amount of treatments are outrageous, you may not be able to recover all of the damges (by settlemetnt or trial). Don't over do it! If you are treating with a provider whom you suspect is intentionally trying to pad the medical bills, go to someone else.