The nature of your work and your income are important factors in determining your policy premiums. People in manual labor will pay higher premiums per dollar of coverage than people in office-oriented work. Each insurer has an occupational manual with different categories. When you apply for a policy, you'll be assigned into an occupational category with a risk rating. If you change jobs and move into a less risky occupation, you can apply for a classification change and, possibly, a reduction in premium.
Your job might also affect the definition of disability in your policy. An "own occupation" policy defines a disability as the inability to work at your regular occupation, even if you still might be able to work at another occupation. For example, a surgeon with hand tremors who takes a job as a medical school lecturer would be eligible for LTD benefits under an "own occupation" policy because he can't perform the duties of his own occupation (surgery). The other option is an "any occupation" policy - to qualify as disabled under this policy, you must be unable to work at any occupation. This is a harder policy for claiming benefits, but it's also usually less expensive than an "own occupation" policy. We recommend "own occupation" policies for most people, particularly those in specialized occupations.