When do you become immune to topical antibiotics such as clindamycin and erythromycin for acne?

Varies: You MUST NOT use antibiotics -- topical or systemic -- as the sole treatment for acne. They need to be part of a combined treatment with topical benzoyl peroxide, salicylic acid, or a retinoic acid derivative. Do this, and you may be able to manage on a combined regimen. If this fails, consider a systemic tetracycline or isotretinoin. The latter works but isn't for the faint-hearted.