I work in insurance and as a freelance writer I've spent the last year writing test prep questions for life and P&C exams, so I'll take a swing at this one.
Life insurance companies have to take particular precautions to make sure that there is insurable interest at the time of the contract. After that, it's all up in the air. The only real teeth arise when they can prove that the initial contract itself was fraudulent. Even then, however, a contract is a contract and it's tough for an insurer to wriggle out of it. It's no easy feat to enter litigation intending to withhold funds from a grieving family and expect to pull it off.
When Bruce Lee died, he had a rather sizeable life insurance policy that was only a couple years old. (After all, he died in his thirties.) However, it was found that he lied on his insurance application. Bruce Lee was an enormous pothead, which not many people know.
The insurance company learned of this and they tried to get out of the contract, claiming fraud. However, after much litigation, they had to pay out anyhow. It was their fault they entered into the contract and did not do their due diligence.
For this reason, the incontestability clause was developed. Insurance companies argue that there was no way that they could make a 100% airtight decision at that initial contact, so they are usually given up to two years to find anything that has gone awry with the initial app. Once that two years is over, the contract is as it is.
The only way there could be a real problem (in my opinion) is if the insurance policy was taken out with a shit company that wrote a contract chock full of exclusions. Even then however, the law still often sides with the defendant.
There's a fancy little thing called the Reasonable Expectations Doctrine which allows the law to hold the company to what the policyholder could reasonably expect, even if it isn't what the contract says. It's not reasonable to assume that you can't smoke a pipe after you begin a life insurance policy, especially when the only study ever released by the US government back in the sixties showed the cigar smokers and pipe smokers live longer than the average person.
While I can make no guarantees, I feel it quite reasonable to say this: if a lawyer gets involved and feels that there is no case at hand, find a different lawyer.