That's correct - 7 to 14 days to get them "over weaning", but not to be put back with their dam.
We keep them seperated until the heifers have been bred (or breeding age as BullLady said). Even at that, they will pair up with their dam & be buddy-buddy - but so far, never had one go back to sucking. Dam has her new calf by the time they are put back together.
Depends on the cow (maybe breeds of cows??). I know Dun has no problem putting them back in 2 months. I KNOW my calves would go back sucking. No doubt about it!
But, I have a neighbor with 1 hereford cow, and she WEANED her calf without pulling them apart (and she wasn't even bred back). I've never tried that, never would even think to try that, so I can't say if my cows would or wouldn't. But, I have kept them together up to 9 months of age (not normal), and went thru just as hard a weaning as at 6 months of age.