I start weaning as soon as all the following are true:
- they're at least 5 weeks old
- they're eating at least some creep (and hay / grass)
- they're in reasonable condition - not too thin, not scoury, not raspy, etc
- it suits me!
By 5 weeks, they'll be on 3 feeds a day; I start by taking out one feed and making sure they have fresh creep and hay available at the time they'd be expecting that feed - usually they turn to the creep as they're hungry and the milk hasn't showed up.
I keep them on two milk meals a day until I am sure they are eating at least 1/2 lb creep per head per day, then if their condition remains good I go down to one milk feed per day. Usually they're only on one milk feed for 4-5 days, maybe a week, then I stop the milk altogether.
If at any time during this process their condition goes backwards then I add back a milk meal for a few days or a week and try again.
I tend to manage my pets in groups of 3 or 4, so they're on a multi-teat bucket or bottle rack system, so the rules get applied with reference to the smallest / youngest / weakest of the group. Sometimes only one needs to get an extra feed for a few days / a week, which is manageable.
I've had a lot more pets this year than previous, and it has been a lot of work managing several batches like this. I am thinking I might try the Shepherdess system next year, where you can run them all together on ad-lib milk, and just take them out into a no-milk group as you think they are ready to wean. (I think you have to start them on ad-lib, you can't switch from 3 bottles-a-day to ad-lib milk or they just overfeed and bloat.) But if I knew I'd only have 6-8 pets, I'd stick with the above regime.