Ummm. they were approved in August and we got our first baby on December 6. Now thats quite a bit shorted than normal. She was premature, biracial, and drug addicted when she was born so several families turned her down which is really sad. We have had quite a few foster children in our home of various ages and yes it is very hard.
Also, it is sometimes hard for the biological children. I'm the only bio child in my family. I was 12 when we started taking children and i had a hard time at first. I'm a lot older now and it doesn't bother me anymore. It's just people have a tendency sometimes to treat the adopted children as "special" and forget about the bio children. As long as they have some special time with you they will be fine.
As to giving up children, we only gave up two babies. One of them had a lot of physical and mental problems and we couldn't handle him at the time because we already had two babies so he went to another family who adopted him. The other little girl went back to her mother. It was difficult but it's worth it once you finally get to keep one.
If you think you have trouble giving them up you could look into emergency placement which has always been very short whenver we have done it. No more than a week or two. Or respite care. I'm not sure if that will be called the same thing where you live but here it is when one family takes another foster family's children for awhile. For example, my mother had cancer last year. When she was having chemotherapy our kids went to another family for a week because i was in school and she couldn't handle them. Those placements are short term and you'd be dealing with another foster family instead of a biological family so that might be something you'd be interested in. But again, i'm not sure how things work over there.
Hope that helped a bit.