Best practice is as little as possible
Generally between 5 days and 4 weeks is standard.
Some companies say that if you give us 6 weeks notice we will guarantee that you can have time off. Others say that only two people in a team can be off at the same time.
But best practice is to allow people time off when requested. This keeps morale high, attrition down as well as lower absence.
It is then the job of the planning team to build enough flexibility into the schedule to deal with last minute time off requests, through management, shift swaps and the like.