Plants vs Zombies, how to beat Survival Endless on iPad.

I was able to beat get the Survival Endless achievement on the iPad this weekend. After a couple weeks of trying and sharing tactics with Dave, we finally figured out a way to beat it. He managed to beat it first and shared some of his winning tactics. Here are some screenshots of what it looks like to get to level 40.




This is what my screen looked like after level 40. I was definitely limping.
Key tactics that you can incorporate:
• Before level 10, you should focus on getting sun and use cat tails
• Before level 20, you should ramp up your fume shrooms and pumpkins
• Before level 30, you should have spike rocks
• After level 30, focus on using ice shrooms, pumpkins, spike rocks, and cherry bombs.

You'll notice that I use a V formation because my outer rows always get hammered by the giant zombies. By offsetting them a couple squares, I have a little more time. you'll also notice that I don't fill every single square. I reserve a couple of empty squares just because it gets too expensive to replace things.

The greatest problems you will have after level 30 will be using more sun than you can produce. Doing enough damage to zombonis and the giant zombies. The fume shrooms should take care of everything else. You'll definitely need ice shrooms and bombs.

Anyone else earn this achievement?