You only have a limited amount of time to file a claim under the FLSA. This time limit is called the statute of limitations. Generally, Under the Fair Labor Standards Act (FLSA), you must begin a lawsuit within two years from the date that your employer retaliated or discriminated against you for asserting your rights under the FLSA. The retaliation or discrimination can be in the form of termination. The FLSA does permit the extension of the statute of limitations period to three years if an employer's violation is willful. However, the sooner you file the better. You should consult an attorney as soon as possible to evaluate your claim.
The limitations period on a wage-based claims, including retaliation for filing a claim of unpaid wages with the DOL, is two years from the date the claim arose but three years if the claim arose from an intentional violation of the Fair Labor Standards Act. Although you likely have three years to bring your claim, you are likely better served bringing suit during the two year period to save yourself having to fight over the limitations period.
Time is winding down on your claims and there is little reason to delay your claims further. You don't mention whether the unpaid wages were later paid but if you are still waiting for those unpaid wages then depending upon the details with those unpaid wages you may have to file suit to recover the unpaid wages within the two year period, which means you need to move forward to file ASAP. Talk to a local employment attorney about your situation so you can start moving forward on your claims.