What is the maximum dose or treatment course of topical steroids that you generally recommend to avoid causing systemic adverse effects?

Topical steroids cause essentially no systemic AEs. Dosing is limited by local AEs.

I think you have to be careful with pediatric patients. A mid-potential topical corticosteroid may cause HPA axis suppression in younger skin for two main reasons, wider overall surface area and increased absorption through thinner skin.