I really believe it depends on the environment they are hand raised in, as well.
I got all of mine when they got down to 2 hand feedings a day, that way I could use the time weaning them to bond with them, but they would be off to a good start at being tame.
My oldest is 10 weeks, she is a sweetheart and will step up as soon as you offer your hand. She's very cuddly and loves to snuggle next to your neck. I have wild and crazy curly hair and she loves to get in it and burrow around. She was initially hand fed by a sweet heart of a lady who had one clutch of babies to deal with, and lots of time to give them attention. She loves to be near me, my husband and even my little 4 year old grandson. She will nibble but never really bite.
My other 3 lovebirds like to play hard to get. 2 men hand fed them before I got them - they have a huge aviary with over 500 birds. I don't think they spent much time with them and just scooped them up to feed and put them right back in the cage. They are still a little leery of my hand, but I can easily pick them up and none of them bite at this point in time, but they are only 6 - 7 weeks old. They also like to cuddle. They don't come to me willingly yet, but seem very content once I force interaction.
I still have my oldest one in a separate cage - we're trying to introduce them over time. I let her out every night while I handle the younger 3. She jumps all over the place and occasionally tries to peck the younger ones, but I just put my hand between them and she stops. I am hoping to cage them together soon, but will do it slowly, by putting her in the cage with them for a few minutes at a time.