The cycle sets the ceiling
Skin renews on a cycle. Cells form at the base of the epidermis, travel up, flatten, die, and shed. In your twenties that round trip takes roughly four weeks. It lengthens as you get older, which is most of why skin looks duller at forty-five than at twenty-five on the same routine.
Every resurfacing treatment (the HydraFacial's peel pass, an enzyme, dermaplaning) removes cells from the top of that stack. Do it once a cycle and you are taking off cells that had finished their job. Do it twice a cycle and you are taking off cells that had not, and the barrier underneath is thinner for it.
That is the single most common way people waste money on their face, and it is usually a spa that talked them into it.
What twice a month actually buys
A brighter face for about seventy-two hours after each appointment, a compromised barrier by month three, and often a rebound in oil production because the skin reads the constant stripping as damage. Then a course of repair treatments to fix it.
The honest version is one substantive treatment a month, with LED in between if collagen is the goal, because light does not remove anything.