Q: How long should X be? (X ∈ chapter,Report,Seminar,Thesis)
A: As long as is necessary to make it convincing.
Q: When is Y due? (Y ∈ Report,Seminar,Thesis)
A: Check http://www.cse.unsw.edu.au/thesis/
Q: How much time should I spend on my Thesis?
A: 18UC ≅ 450 hours (cf. 40 hours for typical assignments)
(But, generally, the more time you spend, the better the outcome)