Waterboy,
We wean at anytime from 6-12 weeks dependant on
Condition of piglets
Condition of sow
Need to get sow back in pig
With a small strong litter which have been fed well by the sow, you can wean earlier.
With a larger litter generally it is better to leave until later.
But alongside this you need to be watching the sow.
If the sow is badly losing condition (despite extra rations), then we would generally wean earlier if we can, then give the sow a month off to recover condition. Some sows put everything into their young, and feeding extra just means she puts more into them.
If she is coping well, and you are on no hurry, then it is fine to leave the piglets in there - but do monitor her condition to ensure they are not sucking the life out of her. If she starts to go thin, then I would suggest if the piglets are fine that you wean.
If you have some smaller ones in the litter you can also half wean, leaving the weaker ones with mum longer. This reduces pressure on her, and gives the smaller piglets better access to milk, so they tend to come on stronger.
As with all things piggie, there are no set formulas, just watch condition of sow and piglets and you'll be fine !