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As there is not offical statement on the card limits, at worst there would be some programming related limit. At the very worst this number of cards would be stored in and signed 8-bit number variable, putting the maximum number of cards at 127. Most likely the number is at least 8-bit unsigned integer (because you can't have negative amount of cards), putting the maximum at 255.
As a journalist, you can create a free Muck Rack account to customize your profile, list your contact preferences, and upload a portfolio of your best work.