I don't take the process of starting an RP lightly. I was probably working on the OOC for my Danganronpa RP for a full month or two in advance before the RP itself went up. I experimented with formatting, jotted down notes about the story, and just made sure this was something I was going to be interested in. I also PMed people with Danganronpa characters for avatars to talk to them about Danganronpa itself. Danganronpa is a very divided fan base, and getting input on what the forum locals liked and didn't like about the franchise was important. Some of these people even chose to join the RP, and are still with me. While I normally wouldn't go get forum user feedback, I do think this has the added advantage of creating loyalty. The most important thing to a RP's success is loyalty, and this process is definetly something I'm going to do with future projects.

Until I arrived at this forum, I never used an interest check. But like Budda, I was pretty much done with it on the first day, and I had my OOC all ready to go before the interest check even went up. I didn't have much presence on the forum at the time, so I thought an interest check was a good idea. However, I did not post the character sheet in the interest check. I did not want to track character sheets between the interest check and the OOC. As a newer RPer with few connections, I think it helped generate interest. 

It was about a week after opening up the main RP thread that the first IC went up. I don't think that's an unreasonable time to wait, but I wouldn't wait much longer than that. Mind you it took everyone 2-3 days to get their characters approved (I have a very convoluted character registration process for this on) But I think I did alright, because everyone stayed the first two weeks, and the second drop off happened about a month or two in. The real reason it took so long to write the IC was because the bad guy personally mocked every character in the story, so there were 17 "roasts" distributed among all the player characters. I think if your first post is amazing and gives people a lot to work with, they will forget the 4-5 day wait until it opens. What you don't want to do is refuse to open your RP because you don't have the perfect number of starting characters. The honeymoon glow of a new RP will start to fade, and people will leave. I mean, some people always leave. But if you start your RP before that happens, people will leave much slower.

Most successful RPs conclude after a year or two. Starting the RP a few days faster in the long run means very little. The important part is captivating everyone's interest and forming bonds that will last the life of the RP. The important part isn't how fast you start, but how eager your players are to start. If no one has faith in your project, a fast start won't save it.