More specifically, if you start April and you won a game in March, you'd have your March win bonus card, in addition to the objective cards that you'd have for April. If you lose early April and have to play late April, you'd use the same March win bonus card and April objectives, rather than drawing more cards from the Legacy deck. Cards are only discarded/destroyed when they're replaced or a game effect tells you to.
Example (February spoilers):
[o]February starts you off not just with the (replaced) mandatory objective from January (cure the three curable diseases), it adds two optional objectives (six military bases, eradicate a disease) and wants you to complete one of those optional ones plus the mandatory one. You might also have a January win bonus if you won a game in January.
If you fail early February, then you'd still have the mandatory objective, two optional objectives, and January win bonus. You don't get rid of any of them.
If you manage to win a February game (early or late), then you'd get the February win bonus card. Whether you do or not, at the end of February you'd get rid of the January win bonus card because it says it's only good for February sessions. You still keep all three objective cards, because nothing has told you to get rid of them.[/o]
Example (February spoilers):
[o]February starts you off not just with the (replaced) mandatory objective from January (cure the three curable diseases), it adds two optional objectives (six military bases, eradicate a disease) and wants you to complete one of those optional ones plus the mandatory one. You might also have a January win bonus if you won a game in January.
If you fail early February, then you'd still have the mandatory objective, two optional objectives, and January win bonus. You don't get rid of any of them.
If you manage to win a February game (early or late), then you'd get the February win bonus card. Whether you do or not, at the end of February you'd get rid of the January win bonus card because it says it's only good for February sessions. You still keep all three objective cards, because nothing has told you to get rid of them.[/o]