AI writing tools show up on lifetime deal sites constantly, usually with a countdown timer attached. The timer exists to stop you asking questions. Ask them anyway. Each takes a few minutes, and any one of them can turn a bargain into a dead purchase.
First, the credit cap. Almost no AI writer can offer unlimited generation for a one-time price, because every word it produces costs the vendor money at the model provider. Find the monthly word or credit allowance for your tier and compare it with how much you actually write. A cap that resets monthly is fine. A cap that never resets is a prepaid bundle wearing lifetime marketing.
Second, which models you get. Listings like to name the newest model in the headline. Check the tier table to see whether that model is in your tier or reserved for higher ones, and whether the vendor commits to future models or only today's. A tool stuck on an older model ages quickly.
Third, whether you can bring your own API key. This is the best single sign for a lifetime AI deal. With your own key, you pay the model provider directly for usage and the vendor's running cost for you drops close to zero. That is a business that can survive selling lifetime seats. A tool paying for all your generations out of one payment has to either cap you hard or change the terms later.
Fourth, how old the company is. Look for a founding date, a public changelog and a product that existed before the deal. An app launched weeks before its lifetime campaign is using buyers as seed funding. That can work out, but price in the chance it does not.
Fifth, the refund window. On AppSumo, most marketplace deals are refundable for any reason within 60 days. Other deal sites set their own terms, and some are much shorter, so read the policy on the specific listing. Put the deadline in your calendar the day you buy.
Finally, compare it with a plain chat subscription from one of the big model providers, which already drafts well. The lifetime tool has to beat that on workflow, templates or brand voice features, not on raw writing.
The short version: buy an AI writer lifetime deal only if it lets you bring your own API key or has a monthly cap you will not hit, the company has some history, and the refund deadline is in your calendar.
