A. If the lender is licensed to make loans to Illinois residents and the loan is a "closed end" loan (a true payday loan) the loan can be enforced for 10 years from default or last payment, whichever is later.
If the lender is not licensed in Illinois it is not enforceable. There are companies making high-interest loans over the Internet without a license.
Some high-interest lenders with Illinois licenses were making revolving or "open end" loans. The statute on these is 5 years and there are probably multiple violations of law.