There is no limit to how many years you can carry foward the unused capital losses. If they can't get applied in the current tax year, then they get carried forward every year until you are able to use them.
Capital loss carryover. If you have a total net loss on line 16 of Schedule D (Form 1040) that is more than the yearly limit on capital loss deductions, you can carry over the unused part to the next year and treat it as if you had incurred it in that next year. If part of the loss is still unused, you can carry it over to later years until it is completely used up.
https://www.irs.gov/publications/p550/ch04.html#en_US_2015_publink100010729
There is no limit to how many years you can carry foward the unused capital losses. If they can't get applied in the current tax year, then they get carried forward every year until you are able to use them.
Capital loss carryover. If you have a total net loss on line 16 of Schedule D (Form 1040) that is more than the yearly limit on capital loss deductions, you can carry over the unused part to the next year and treat it as if you had incurred it in that next year. If part of the loss is still unused, you can carry it over to later years until it is completely used up.
https://www.irs.gov/publications/p550/ch04.html#en_US_2015_publink100010729