what has writing/producing those really short (<= 10 seconds) songs done for you? I'm doing that now because I am really bad at developing a melody but really good at coming up with a short melodic phrase and producing it to sound really fun and interesting. I think it is making me better somehow. I would also like to know how you learned to create longer songs that develop the melody and go to other places. It's hard for me to write stuff that doesn't "end" as quickly as it started.
the reason for doing this when starting out is simple. especially when working alone, the riddles and challenges grow exponentially with the piece length. so it's gonna get real hopeless real fast if you are trying to learn everything all at once. My advice for something longer, at the risk of being very obvious advice, i would suggest increase the length in extremely small increments. make each one 1 second longer. i think you will learn a lot