I dated 6 MPAs in the last 10 years and recently coming off a relationship with another one. My relationship with them last anywhere from 4 months to a year. When I mean relationship, I mean girlfriend type relationship, I met their families, going out for dinner with their brothers, sisters and daughter if she has one. Of cause I will not mention anything about her job when I am at their family getherings such as thanksgiving dinner, X'Mas dinner and etc.....
Over my 6 relationships, I never have to support them financially at all. However, when we go out for dinner, I pay most of times and never have to buy them gift unless it's her birthday or X'mas or whenever I feel like then I will buy them some small gifts, I got the same return as well. These MPAs, they were pretty and young, they met so many men everyday not only at work but just about everywhere they are. It's hard for them to settle down with one guy for a long period of time. I do keep in contact with some of them now and then. Most of them have 3 or 4 different b-friends since we broke up. Only one wanted to marry me but she has a daughter so it didn't work out as I have never been married and wanted to have MY OWN KID.
A truly long relationship with an MPA is not impossible as they are human being as well, they need love like you and me. But like I mentioned, they are young and pretty, it's not easy to stay with them for a long period of time unless they change their occupation.