I find it varies greatly. One was a couple of months. Another was a couple of years. And there have been plenty in between.
I suppose it depends on each child's own issues (medical problems, mental health, family background) as well as things like the age of the child.
Also, as horrible as it is to say, a pretty face goes a long way.... I've had adoption social workers ask me to retake photos that were going in adoption magazines because the child "didn't look particularly appealing" (I'm paraphrasing but it was along those lines). Sadly that child was probably the loveliest I'd cared for as well!
Have seen many many of our LO go too for ever family's over our 38 years of fostering all with 100% success , Part the public do not see input foster parents put into these success as a result of years of experience they contribute too the adoption process, preparing a child accessing support, training and early interventions parenting skill's , all part of mandatory and on-going training we all have too do. We have to do 3 post training sessions a year attend training support group sessions once a month, bet no sw has too do this.
At the moment, I feel as though I will need to be strong and support my DH and own kids. They will be heartbroken. That, and having to be supportive,encouraging and enthusiastic towards new parents, is going to leave me drained. And after she leaves I will grieve.
Every placement too for ever family for us all is the same very emotional and upsetting, again an area which needs support and attention. Only just last week got back from final intro no social worker present or support just me and new family for 7 days. Had too stop on way home for a little weep several times. Still child is very happy and settling well. We are fortunate that another placement came too us within a few days, this has been the trend for some time. It helps a lot as attention is placed on new baby's/children. Last child was with us for 2 years from birth so understand how emotional it is for you and us all.