Apple’s Intelligent Tracking Prevention 2.1 causes cookies to be only saved for 7 days unless the Safari user directly interacts with the website again.
There will be no issues
Could be issues
With ITP 2.1, all persistent client-side cookies, i.e. persistent cookies created through document.cookie, are capped to a 7-day expiry. This causes cookies older than seven days to be destroyed, which leads to the user being identified as a new user who hasn't seen the site before.
The following resources provide more information: