If I'm viewing my footage in half resolution to ram preview, will this affect the 1080p quality I have the composition set as?
The RAM Preview stops at about 10,000 frames. I have a 18 minute video in 1080p that I need to render out. The ram preview does not render the entire thing. Is this a problem? What could I do?
RAM preview has nothing to do with rendered output. If you have edited an 18 minute movie in AE you are not using the software as it was designed. AE is for creating shots or short sequences. Most of my comps are under 10 seconds. A few are a minute or two of a sequence. Editing is done in a NLE. That is where I edit my shots and sequences to perfect the story. Trying to edit in AE is nuts.
If you really need a longer preview then you can either skip frames or set a lower comp resolution.
As Rick said, there is no problem. You just don't understand what AE is for and how it works.