Not an official answer, but here's the wording on the card:
Keeper Limit 2
To play this card, place it face up in the center of the table. This rule goes into effect as soon as you play it. Discard the previous Keeper Limit, if any.
If it it isn't your turn, you can only have 2 Keepers in play. Discard any extras immediately.
You may play new Keepers during your turn as long as you discard all but 2 at the end of your turn.
Any time a card says "may" then you are allowed to do what it says, but you don't have to. The only "may" that really applies then is the "you MAY play new Keepers..." but that's always the case.
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