"Keep coming back" assumes a cure was ever promised. Two published statements put a boundary around that assumption, and they are short enough to quote.
Reduces, not prevents
Cleveland Clinic says practicing good hygiene and foot care reduces the chance toenail fungus will come back. The verb is "reduces." It does not say prevents, so a return is not ruled out by doing everything right.
What treatment claims
MedlinePlus says medicines clear up fungus in about one half of the people who try them. Hold that figure next to the Cleveland Clinic one. One describes how often a treatment works, and the other describes how foot habits change the chance of a return. Neither promises a permanent result.
More detail lives in the primary sources. The AAFP page on onychomycosis and the review Onychomycosis: Old and New are the clinical reads. Cleveland Clinic's page on causes and treatment and the MedlinePlus entry on fungal nail infection are the plain-language ones.
What to confirm, and with whom
Ask your podiatrist what counts as cleared, how they will check, and what the plan is if the nail looks affected again. Readers around Itasca who have already been through one round should say so at the visit. Keep the instructions for hygiene and foot care in writing.
The clause readers tend to skip
"About one half" means the other half did not clear. Anyone offering treatment should be able to tell you that number before you start, and what happens to people in the other half.