How long to try treatments?

[Imapsomom]

How long do you try treatments before deciding they are not working? My son's scalp psoriasis is suddenly quite bad, worse since starting with the extra strength tgel shampoo, but also in the same week as starting tgel had a very stressful event, and ate unusually poorly for a week so I am not sure what caused the flare up.  He was diagnosed with Glutate about 6 months ago and proscribed clobetasol which worked with in 2 weeks (but it all came back and more). Now 2 weeks seems to be my marker for 'working'. Tried to switch from Clobelosol to Dovobet but saw little result in 3 weeks so stopped. We have an appointment to see the dermatologist in 4 weeks, but he is really pushing the Biologics and my son is only 13 so I think much to young for such a treatment. I would love to calm that scalp down (and the rest of his P) but don't know when to give up on a treatment and try something else.