In general, Visa transactions allow the acquirer 30 days from the date of the dispute notice to submit a response. MasterCard transactions allow the acquirer 45 days from the date of the dispute notice to submit a response. However, payment processors will often set their own due dates to ensure they have enough time to process a response before it is sent to the network for review.
It is recommended to send your response to your acquirer no later than the halfway point of their time limit. E.g., Your acquirer should receive your dispute response no later than 15 days from the date you received the dispute notice.
American Express (a.k.a., "Amex") and Discover are unique in the fact that they act as both the issuer and acquirer. These networks will set specific due dates in which a representment (i.e., a dispute response) must be submitted.