In my opinion, this cash out feature is pretty much the worst thing there is.
On the one hand, it influences the playing behavior of some, as you yourself have noticed, and on the other hand, there is only one beneficiary in the long run, the operator who charges a fee for it; everything else is regulated by variance anyway if you play more often.
I also notice that this option is mostly used by recreational players, rather than regulars.

I'm now almost at level 2 in the promotion, and I should reach level 5 by the end of the month, but I probably won't make it to level 6.

Basically, though, NL10 should be easy to beat and therefore well suited for generating additional rake for the promotion.
I wish you a good hand.