No rule says you must continue, but the sources describe results that fade and an upkeep pattern that follows. Count that pattern before the first session.

Why results fade

The American Academy of Dermatology gives the mechanism: "As your body loses collagen, the results will fade. People lose collagen at different rates."

The second sentence is the useful one. No one can give you a single expiry date, because the rate differs between people.

The series, then the maintenance

For the first stage, the American Society for Dermatologic Surgery says: "Typically a series of monthly treatments (at least three) are required for optimal results."

For afterward, the Academy says: "To maintain your results, your dermatologist may also recommend that you return for a maintenance microneedling session once a year."

Together that is at least three monthly sessions and then a possible yearly session. "May" keeps the yearly visit a recommendation, not an obligation.

Pricing the real commitment

Price the series plus a yearly visit, not the first appointment alone. If you stop after the series, the fading the Academy describes is the trade you have accepted.

For further reading, the Society has a microneedling page, the Academy explains how microneedling can fade scars and uneven skin tone, and PMC hosts a systematic review of radiofrequency microneedling for facial rejuvenation.

So, forever?

Forever is not required and yearly is not mandatory. The sources support a series up front and an optional annual session, so ask your provider which fits your goal.