Do some math. The scale is linear ... how long is it going to take to get your BTC back? Ever? The tiny amount of bitcoin you are getting will be less all the time ... as the pool size grows your reward goes down.
If you really want to get BTC from mining, mine scrypt. I recommend scrypt.cc. The growth of the network and pool are much more spread out and you can really actually make some Bitcoin. When I left CEX.io I was down by .5 BTC. Now I'm ahead about 3.2 BTC in a couple of months.
At CEX.io, you have to trade to make money and now you'll have to pay to trade. It isn't worth it, go west to scrypt mining. At least do yourself a favor and look at https://bitcointalksearch.org/topic/scryptcc-scrypt-cloud-mining-444495. Any you don't have to use a referral link to join unless you want to. Anyway there are many people starting out there with tiny amounts.
I put my 13 year old son there (with a little help) and he making something like .0008 BTC/day now. He got a big boost from selling some faircoin.