I didn't have a save on level 5 after I beat the game and I found the strategy on level 2 to be extremely slow. There's another infinite spawn point right at the beginning of level 1 and it's much faster than the level 2 spot (and quicker to get to).
From the beginning of level 1: Dig down -> Dig Right -> Jump over pressure plate column -> Jump up 2 stairs and you are there. There's a row of rocks you can jump on that spawns mobs out of either side two at a time. Two on the left, two on the right, two on the left, etc. I just sat on the left side and killed the mobs over and over. Works the same as the Level 2 place but spawns much quicker.
You might be able to jump back and forth to do it quicker, but that didn't work well for me.