Right now, the minimum fee to get into the next block is 490 s/b. An input is about 180 bytes, so each input will cost about 0.0009 BTC to send.
That means that if you set the threshold at less than 0.0009 BTC, you will not be able to send the money anywhere because the fee will be 0.0009 BTC (about $12) for each time you cashed out.
It's very sad that many people acquired small amounts just to get started and now they own worthless "dust". Dust is the amount that can't be sent because the fee is more than the amount. A few years ago, 0.00000546 BTC was considered dust, and it was worth a few hundredths of a penny. Now the dust amount is $12.
Thanks, I remembered mining years ago and cashing out with tiny fees and I forgot how much higher bitcoin has gotton (and the fees must've risen with it).