Final answer:
The major medical deductible carryover period usually pertains to the final three months of the plan year, which assists in applying late-incurred expenses towards the next year's deductible.
Step-by-step explanation:
The major medical deductible carryover period normally applies to expenses incurred during the last three months of the plan year. This feature is important as it allows for expenses incurred near the end of the plan year to be applied towards the next year's deductible, ensuring that patients do not have to pay their full deductible again immediately after the plan resets. It is a useful benefit for those who incur medical expenses late in the year and can be a deciding factor when selecting a health insurance plan.