I'm thinking of buying extra gpu cards for mining. Doesn't anyway one know the approximate time to make 1 ethereum with These cards
On 03.02.2018 I was making 0.05ETH in 69hours with 5 x 1080ti with ethminer at 38h/s per card.
Your hashrate is very lower at 38h/s, other software would yield a different hashrate,
Maybe ethminer is only showing a lower hashrate than it's actually mining.