To go off Zephrya's point-- do not just settle. Maybe if you're looking for a quick one-shot, sure, take the risk. But taking on a long-term partner requires a lot of communication and a lot of similar outlooks in what you want to see happen in a story.
I'm quite certain that all my current long-term partners want similar things and enjoy a lot of the same themes and concepts I enjoy, we wouldn't have worked out this long if that wasn't the case, and all of them are very open and communicative. These are very important factors to me but everyone is different, I know of some partnerships where there's almost no OOC communication and it works out for them so... power to them I suppose!
It's just more about finding your niche amongst the sea of writers on here.
Another thing is to not give into things that make you very uncomfortable. This is different from compromise in many ways.
For example, I'm not particularly fond of playing women with very large breasts, but I have some partners who very much enjoy that, I compromise and play them if they do something for me in turn-- this is how I'm able to make something I'm not too wild about long-term sustainable. But something I'm very much adverse against, let's say for example, Incest-- I will never compromise or bend on this rule. A potential partner who continues to try and squeeze in themes or concepts I have made extremely clear I am adverse to is not worth keeping around. If they can't be bothered to respect your limits, your time and what you value they are not worth investing long-term into.
Partners who understand motivation delays, work, real-life issues are the ones you will want to keep around. All of my partners are very understanding and don't give me any back-handed sass if I have to take a month or two hiatus at times, these are the types of partners I highly recommend keeping!
RPing is a two way street (well, most of the time!), so make sure that you both are enjoying what's going on and where the story is heading.
Long story short, it's really just about finding those partners you click with and sticking with 'em, don't settle for less or people who won't put in the same amount of effort as you do!