Duet is free to download, and the price you pay depends on two choices: the tier, Premium or Supreme, and the length, which is one week, one month or three months. The store listing is where the actual figures appear, and they change, so read them there instead of trusting a number in an article. What an article can do is tell you what each tier is for and whether it is worth buying.

What is free

The app costs nothing to install, and the store listing shows in-app purchases for everything beyond that.

That structure matters for a practical reason. You can set up an account, look around, and see how many women near you are actually active before spending anything. A man who pays on the first evening has paid for a guess.

What Premium adds

Duet Premium gives you the ability to see who likes you, unlimited likes and unlimited rewind, among other perks.

Of those, seeing who likes you is the one with real value. A like from a woman is the cheapest attention you can get on any dating app, since she has already decided to say yes. Unlimited likes and rewind are conveniences. They save you from running into a limit on likes or from regretting a pass, and neither of them changes how many women find you attractive.

What Supreme adds

Supreme includes everything in Premium. It adds message before matching, which lets you send Praises directly to people you like. It also adds advanced filters by height, education, purpose and popularity, and Daily Picks.

The most useful of these is the message before matching. It lets you write to a woman before she has liked you back, and that is the one place where what you write does the work a picture normally does. If you buy Supreme, treat each Praise as scarce, and write something that could only be sent to her.

The one-off items

Duet also sells items on their own: Crushes, Turbos and Praises. Its terms say these have no cash value and are non-refundable once purchased.

These are the easiest purchases to make on impulse, and the hardest to justify afterward. A small one-off charge feels harmless, and a handful of them in one week can add up to more than the subscription would have cost.

How billing and refunds work

The store listing says Premium and Supreme purchases are charged to your iTunes account. They auto-renew unless the renewal is turned off in the app 24 hours before the current period ends. A one-week term is the one to watch most closely, since the renewal date arrives quickly.

Duet's terms add that if you stop using the app during a paid period, Duet is not responsible for refunding the fee for the remaining period. So a short term is a way to limit what you can lose. Buy the shortest term that lets you give the tier an honest test.

Which term to pick

The listing sells Premium and Supreme as one-week, one-month and three-month subscriptions. The shorter the term, the less you commit before you have seen a result.

A one-week term suits a test, since a week is long enough to see whether women answer you and short enough to walk away from. A three-month term only makes sense after you have already seen the tier work. Buying the long one first is a bet that you will like it, placed before you have any evidence.

Whichever you choose, set a reminder for the day before it renews. That one habit saves more money than any feature does.

Is it worth paying

a dating coach's approach to paid features is a good one to borrow. He rejects the idea that you should never pay for anything, and says it is a bias that costs men results. He also rejects paying blindly. His method is to try an individual feature, particularly an inexpensive one, and see whether your results improve. If they do not, drop it.

Run that test on Duet in concrete numbers. Count how many women write back to you over a week on the free version, then buy the shortest Premium term and count again. If the count rises, and some of those chats become plans, keep it. If nothing changes, you have your answer for the price of a week.

Do not buy Supreme to compensate for a weak profile. Advanced filters and Praises cannot fix a picture that does not show your face, or a few lines that sound like every other man. Fix those first, since they cost nothing, and then decide what the money should buy.