These days it is typical and normal to promote yourself, to have more than one agency, and to freelance and market yourself yourself.
Many aspiring models, and girls who want to model think that by having an agency that their dreams and pursuits will launch and they will be working consistantly as a model. This doesn't always happen.
An agency might only call you a few times a year, a few times a month, or it could be every week, but the more experience you have, and the better your modeling portfolio is, and the more you can show you can model the more you will be used.
I have found it is best to have some tearsheets, have some experience before you approach a modeling agency. If you expect to be discovered from your modeling page on a modeling website you are wrong. You need to have your marketing tools, headshot and compcard, and you have to be mailing it out and trying to improve your modeling portfolio and a big thing girls forget is diversity. I think being diverse is very important. Being able to model a handbag, and also be the face of a tampon commercial. Seriously! Modeling is more than fashion and maybe before you start to think of agencies, and photo shoots you should ask yourself,
" Do I have the will to promote myself and get the photos and tools I need to do so?"