There's been a lot of good advice given here. There are plenty of people who prefer shorter posts.
What it takes, IMO, is patience and perseverance to find partners that you enjoy writing with, and who enjoy writing with you. Sometimes that also includes a little bit of give and take -- the more you limit what you are willing to do/want to do, the more you limit the number of potential partners.
There are ALWAYS people who will just disappear on any internet endeavor -- and even in real life. It's a fact of life.
You can limit that yourself in some ways by taking some time to do research. Elliquiy has some wonderful tools available to see the posts of potential partners, provided they write on the forums. Use it. You can see what kind of posts potential partners usually write, their posting frequency, and how their games progress. If their posts are longer than you're comfortable with, then if you're interested otherwise, you can reach out to them to see if they would be interested in writing shorter posts. Many people here are very versatile in style, and in post length.
Yes, it may be a bit of work, but it increases your chances of finding those 'good fit' partners. And don't wait for them to contact you -- contact them. Say hello. Interact with them on the socializing boards. If you see someone's writing you like, compliment them on it. Start a conversation.
I've found some great partners that way. Yes, some have still disappeared off the face of the earth without a word after a while, but I still had fun.
I suppose it all boils down to what's fun for you and how much you're willing to invest in it. There is no magic formula -- do this and they will come.
I sort of wish there were.