I think it depends on the case and earbuds battery life as well as cable and charger…
If the case is at zero and the earbuds are at zero, the charge will have to charge the earbuds and case which means a longer time to charge than you may thing they normally did. If you start to charge at 1 dot, the one dot could be anywhere from almost zero to 30 percent.
If it is not at zero (all three dots not lit when opened) then the issue may be the cable or charger is going bad if it taking like 5 to six hours as I would think around 3 or 3 and 1/2 would be about right for earbuds and case at zero percent. Try a different cable and/or charger if it is taking like 5 hours to charge or more.
Worse case it is the case and you can contact support for that if needed.