It depends on how long you see the product lifespan, how fast and whether you develop it and release new versions at all, does the technical support you provide apply to all versions of the product? (in my opinion this is a bit crazy, unless you have a larger team). Does the license apply to the version you are currently selling or to all future versions you will produce? There are many variables that can be taken into account to have a bit of an advantage, putting the customer in a situation where: technical support applies only to new versions of the product (and you set the rodmap yourself so you can go far away from the features they liked when buying your product - thus not supporting them), offer custom work on the product, technical support for old versions - to be considered if at all possible. It may turn out that the one-time purchase cost for the customer will be more expensive than the renewed license.
If I had business concerns, I would talk to users and try to understand why some pick recurring payments and why others pick one time purchases.
Then I would reconsider my offerings based on how each group provides or does not provide business opportunities.
Anyway raising the price of the lifetime product is the simplest way to encourage price sensitive customers into recurring plans. If that doesn’t change their choice, revenue increases.
Do the math - say you get 1000 customers who buy lifetime deals. And nobody else. How much does it cost you to keep the product alive for those 1000 customers, and how long is your runway using the money from those 1000 deals at that cost? Is that runway an acceptable "lifetime" in the view of those customers?
If you get good answers from that math, maybe it makes sense. But I'd wager that most business models don't have good numbers in such a scenario.
Is a 'lifetime deal' what we old timers used to call most consumer software license purchases (where you bought a package at Best Buy for $30 and that version worked on your computer for as long as you wanted)?
Assuming your product is for individuals, I would listen to my customers, and move away from services and towards the "purchase once" model of old, guaranteeing maybe 1 or 2 major updates.
If your product is for business and production, I would simply remove the lifetime purchase option.
My product is for businesses but they seem only interested in a cheap lifetime price. I guess adding more features is the solution here to get them to pay more.
Have you asked them if they would pay more for more features? Perhaps some work to be done around perceived value and pricing, and to understand if putting more resources in is actually going to generate the revenue lift you’re looking for.
Do you have 20+ lifetime sales to show this is true?