None are as unworkable as Citi's though. Sure, Amex is once per "lifetime" but they also have what, a dozen different MR earning cards each with its own bonus? Chase is once every 24/48 months but they have about 7-8 UR earning cards. Citi's rule locks you out of all TYP sign up bonuses for 24 months and they only have 3 TYP earning cards. It also resets upon account closures as well as new accounts.