There's a couple of things here. First of all the quality of the cigar will indeed matter. The second is that "How much should you smoke" is a question of taste. If you don't like the changing taste after the first third (a cigar is usually split in between three distinct changes in taste) who says you should carry on smoking it. It may be a waste but if you don't like it then put it down.

My advice would be to try and smoke a few different brands and find one you like.

Enjoy!