Your debts never really expire but after 7 years a debt collector is unable to take you to court and sue you for the debt owed.
They also cannot garnish your wages or take any possessions for the debt you owe through court after 7 years have passed.
The debt will not expire and still be there and they might try to continue to collect the debt even after the 7 years but they will not be able to sue you for the debt.