Reliability and failure are statistical. These are normally expressed in mean time between failure as being so many hours, months or years. This means that the more of an item in service in the world, then the more the total number of failures that can be expected, and will actually occur. For any individual card, the lifetime cannot be specified as variations due to for example, the operating conditions, (such as airconditioning settings, power supply tolerance, etc) will have a cumulative effect. An indivdual card may last in service one week; the card that is used to replace it may remain in service for 40 years. All that can be predicted is the rate at which board failure will occur.
If you are concerned about minimizing downtime due to specific board failures, it would be more practical to keep a stock of these critical cards handy for when failure does actually happen.