That’s correct: if you say a package expires in a week then your customers will not be able to use any credits within the package when it expires. However whilst it’s valid they can book any date that is available according to the visibility rules - however far in the future that may be.
A few people have asked about this and I’m just (at the moment) not seeing an easy way of making this work - the main problem being disrupted user flow. At the moment your customers choose the appointment, ts & cs, etc., confirm and pay. Now we’re saying they’re going to get to the payment stage, choose the limited dates package and be told that some or all of their appointments cannot be booked (because they’re outside the dates allowed).
You can set visibility rules so that your customers cannot book more than X days before the appointment if that helps? Select ‘settings’ -> ‘calendar settings’ from the main menu. Unfortunately this is on an organisational level, I’m thinking it might be useful to have visibility rules per service: I’ll have a think about that.