When you accumulate a largish stack deeper in a tourney you have a big weapon which can really help put you in postion to win the tournament. You can take some chances, and keep pressure on the rest of the table. I would pay attention to gameflow and how aggressive/passive or loose/tight the table is. If they are flatting every raise you make then you will need to tighten up your range and play more TAG, but if they are folding a lot, then by all means keep your finger on the raise button. The one spot where you usually can tighten up is right after the money bubble burst. People are going to just look to get their stack in and double up after they have secured a cash, so you can't put as much pressure on them with a bigger stack.

There are plenty of times where you will lose your big stack, but thats just variance. Calling an all in from the button with a9 in the bb is most likely a fistpump call and it's just unlucky if they have you beat. It's spots like these that allow you to continue to build a stack. As for calling 30bb shove preflop it depends on the player. Most of the time players dont just open ship 30bb, but I have seen it and i do call a bit tighter because I don't really want to flip for 30bb each when we have a good edge on the field. I wouldn't get into the habit of folding ak preflop to one player post ante though;)