I usually walk in with a generic prepared essay, just need to tie in with question. In such a case, i'll say about 5-6 pages (50 minutes), or 4-5 pages (40-45 minutes)
yeh, I never write enough in exams. last exam i was so proud coz I got to 4 pages and I got out and everyone else had written like 6-8 pages.
I always stick with the excuse that I have small handwriting.