Hello,
Dandruff/ seborrheuc dermatitis is not like a fever but treat it like a chronic condition like
diabetes. Dandruff is actually result of activity of your normal commensals who get active when they get favorable condition. As there are multiple factors which can trigger this condition, stick to your treatment regime with maintainence therapy.
Next Steps
So if you were getting good results while using ketoconazole, Do not stop all of a sudden. You can at least use it as a maintainence therapy like once every three weeks or so.
Consult me online via practo pro to get detailed treatment of your condition apart from ketoconazole