Debt collectors will often send out letters telling you that they will accept a lesser settlement, but only for a limited amount of time. Like most “limited time only” deals, this is usually not the best that you can do.
If you’ve received an offer like this, and you want to take advantage of it, you can always negotiate that offer. Offer the collectors half the amount, or half the number of payments, and see what happens.
You can also improve your bargaining position by hiring an attorney to negotiate for you. I make sure that my charges for my services are always low enough that you are benefiting from my work for you.