Let your users choose the expiration date by calendar picker. Your users will be able to better control your ads on the most convenient date, including editing the date as often as necessary to move the item to the top.
Admin just need configure/choose the categories to calendar picker appears on publish page.
No need add any hook/functions or code. Will working in any theme.
Theme color to calendar picker: default or dark.
Days to top after xx days (zero will disable)
Expiration mode (to users, or admin define expiration)
Min date on calendar picker (in days)
Max date of calendar picker (in months, max 12)
Expiration field (required or not)
Custom css to expiration field (enable / disable)
Free support, free custom css for expiration field for any theme, if you need.