Limitless vacation policies were popularized in Silicon Valley and have slowly migrated to the rest of the country. Often these policies are adapted by companies trying to recruit “the best of the best,” by offering attractive benefit packages.
It is important to know that the Illinois Wage Payment and Collection Act requires employers to pay out employees for all accrued but unused vacation they would have been entitled to in a given year. It is safest to give guidelines or a maximum amount of vacation that will be paid out.
Another consideration is whether a limitless policy makes sense for all employees in your company. There are often jobs (a receptionist or administrative assistant come to mind) that require physical presence in the office. It is possible to have different vacation structures for different employees, and that is worth considering.