Data loss before changing subscriptions?

I had to cancel my subscription to change my payment method based on what I found in this forum. However I can only make the change once my current subscription expires. Is there any immediate change when the subscription expires, eg. losing LingQs or reading history? I remember getting a pop-up to pay a small fee to keep my data past the expiration but I’m not sure if the data loss is immediate or if I have time after the expiration until I re-subscribe using the new payment method?

You won’t lose anything, no worries. Your data is saved for 30 days after downgrading, so more than enough time to upgrade back.