(Sorry for my English)
When I try to preview my creation, it doesn't finish to render all of the working area. For example, if my working area is 45 seconds long, it just renders until 35 seconds approximately. At a more exaact number, around 1300 frames with a 29,97 frame rate. Please help.
RAM preview (what is from CC2015 called Preview) will render all it can and it depends on your available RAM and how much resources does your composition need to render a frame (effects, animation, 3D+Lights, Motion Blur etc.) . you can try to purge the RAM and see how much AE can handle click edit -> purge -> all. usually what you do to as a workaround is preview different segments at a time. or you could choose to preview only half or quarter resolution and get more of the preview, or skip a frame, or lower the preview frame rate, or even choose to render just a segment of the composition window using Region of Interest. and if all that is not enough and you really want to see the whole sequence at full quality in one go than you will have to render a lossless codec (choose one that can have a decent playback like Photojpeg, not Quicktime Animation) or encode an MP4 one with AME.
more about this here: