Elastomeric paint instructions say a second coat MUST be applied within 24 hours. Is this true for painting over old elastomeric paint also?
Normally all that is required is a clean surface for the elastomeric coating to adhere too. This would be a maintenance coat. You didn't mention brand so I can't confirm the exact requirements. I recommend going to the paint store, that sells the elastomeric, and ask if there are any special requirements for a maintenance coat.