So I've been doing that thing where I try and catch the musical ideas before they fly past and I forget them. But now what happens, is I catch maybe 4 bars and try to get them recorded, but by the time everything's recorded, the spark is gone and all I have are these four bars. Do I just need to work faster?
no, i think you're doing fine. it's not expected that you can get much further than 4 bars at one time. What i think is the right thing to do here is, properly file and label your item into a list, and then carry on with your life. A separate question, for several different departments at different times, is why when and how to do anything with them, and also when and how to decide which, and a whole splintering of other questions which i would be glad to help you with as well, if you are ready to examine what your goals may be