Novel =/= Short story

So, I've been writing since I was very young.  The problem has never been, "What to write about next" - but more along the lines of keeping up with the last thing I wrote about. 

As in, all I ever seem to get are half stories (the longest being about 20 pages). Any tips for actually writing something substantially longer,  instead of ending up with a short story?

Good ones, on the other hand, write the shortest they could, and if they write a novel, then it must be the shortest they could to express a poetic image convincingly and without preaching like a faggot.
>>2 here
That's what I mean by scale, BTW.