When an account expires for whatever reason (e.g. expired card, trial ends) how long should we hold on to the users data before deleting it?

I am referring to all data **except** what identifies them as an existing user.

***edit*** - *The UX aspect is this (as [dnbrv](https://ux.stackexchange.com/users/10478/dnbrv) eloquently put it):* 

> 
> if a user comes back after some time, they might expect their data to
>  be available.
> 
> 
>