The length of time that ice will last in a cooler depends on the quality of the cooler and what type of ice you use.
Cube Ice will last around 1 to 3 days in a well insulated cooler while block ice should last from 4 to 7 days depending on the weather and the insulation of the cooler.
It also depends on how often you open the cooler to get things out.
So the more often you open the cooler the less time the ice will last but the less you open your cooler then the longer the ice should last.
If you want to chill things fast then use cube ice but if you want to keep food or drinks cooler for longer periods of time then go for block ice instead of cube ice.