An insurer who discovers that the claimant treated far longer and far more frequently than he likely should have, considering the injuries sustained, will look closely at the nature and the cost of treatment received. If the treatment is clearly excessive and more expensive than it should be, the insurance company will use that information to cast strong doubt on the claimant's credibility, making him/her look like someone who is trying to treat more than needed and inflate claims for the sheer purpose of increasing recovery. This argument works quite often to reduce a claimant's recovery or event lose the case in court where they otherwise could have won. This is because few factors hurt a party in trial in front of a jury than credibility issues. Once the jury determines or event suspects that the claimant treated more than he needed for improper reason, they likely will doubt the entire claim and won't believe much else of what the claimant has to say on the stand. This is exactly the reason why it's a good idea to avoid getting more medical care than you need for your injuries, especially if your case is likely to go to trial.
You should especially make sure you don't get too much of the treatment that doesn't help you. Therefore, if for instance you treat for a chiropractor for 1-2 months and you feel no improvement in your pain symptoms, you should at least consider switching to physical therapy, acupuncture, etc. This is because it's usually quite hard to explain why a person went to see a particular doctor for 6 months or more several times a week if it didn't help at all.