Here's a video of an almost endless combo:
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If you go to his channel or go through the related videos you should find more.
There are plenty of endless combo setups. Here are the problems with them however:
1. You stop getting points if you repeat a trap. Endless combos are great for finishing stages, but bad for experience.
2. There are often 3 enemies against you at once. Enemies have different immunities and resistances, so its unlikely that you can get all three into the same infinite loop.
3. If you get stabbed by one of the other enemies (or shot at... freaking Nuns with Guns seriously), its very difficult to continue a combo. (You can't activate traps while you're in hitstun).
So overall, its pretty balanced. For maximum points, you must use as many different traps as possible (outside of a single-deployment multihit trap, like the Swinging Pendulum)