Our first attempt at being pregnant ended this way.
I didn't know I was pregnant until I was more than 6 weeks gone. At 9 weeks we had our booking in appointment I mentioned I'd had a little bit of bleeding so they booked us in for a scan. We had it at 10 weeks and there was no heartbeat, an internal scan was done and it was confirmed there had been no growth after 7 weeks. I had had no bleeding since then and the bleeding had been very minimal. Within about half an hour of the internal scan the bleeding started, just as we were discussing options for management - and I had opted for home management as I didn't want to have to deal with any of it in hospital. So the answer to the original question was, in my case, 3 weeks before it started to come away.
Having since been in hospital for bleeding in pregnancy, I think I'd make the same decision again. If it is possible to wait, and if there is no risk to you in doing so, I think I'd give it a couple of weeks to see what happens. Physically it wasn't a pleasant experience and being at home so I could just deal with things myself rather than having doctors and midwifes having me do things the way they thought was best was much better. Even things as simple as going into the shower for half an hour to let the warm water help with the pain, being able to sleep when I wanted to and eat when I wanted to, made such a difference. As long as you have someone who can be there to fetch and carry, I'd go for the wait and see approach. I understand D&C is safe enough as are the drugs but if you can avoid even the minimal risks, that may be preferable.
Don't let the healthcare professionals bully you or influence your decision. Talk to them to ascertain the risks of all approaches and base your decision on what you know is best for you. They tried hard to push for me to go into hospital but I knew it wasn't for me. It is hard to be strong with them when emotionally you are all over the place. If you have someone who is with you when you speak to them, you might have to ask them to be strong on your behalf.
It is an awful thing to have to go through. Our approach was that it wasn't meant to be. That particular attempt obviously had something wrong with it and better to know at that stage than to find out much later. I know that kind of thinking won't work for everyone, but it helped us through the process greatly.
I hope whatever you choose, it works out ok for you.