Live Tournaments, when is it not worth while?

[winky51]

I like to play live tournaments but I don't have the big money to enter a bunch of $500+ tournaments. I have to settle for $100-$200 entries. So when is it that a tournament is NOT worth entering because the structure makes it more of a crap shoot?

Usually the tournaments I enter are the following:

4000 chips
25/50 blinds
blinds go up every 20 minutes.
House takes 20% $130+$20 buy in for example.

I usually play tight to build the tight image and try to stay on the table that doesnt get broken up. I want my opponents to fear me. The more chips I have the more I steal and play more hands. Because of my image I get away with a lot. But I find that I basically have to win a bunch of all in hands by the lessor players to survive? Because they just blantently push with crap all the time putting my stack at risk. I find I have to double up quick to play more hands to give myself more chances to win more chips but if I get no cards before the blinds rise I'm screwed. With 20 min blinds you can get SS easy.

Thoughts of if I should play these live tournaments? Could a change of style from conservative be in order? The players suck 90% and only think about their hands not anyone elses.