when will we found a block in ETH mining ?

Nobody knows never how much effert is nessecary to find the next block.

With 100% we had to find the block within the next seconds. With 200% we need to wait 2 more weeks.

If we look from the first day of the pool till now we had a lot of luck - only 67% effort. In a year, be sure, we will have an effort between 98% - 102%.

Edit:

I have ~115 T Shares... - doesnt matter...

We are probably over 100% effort already, so the block is due. It might come anytime, but like Opa said, it's also possible we might have to wait another 2 weeks.

Does that mean that we get less ethers when it takes up to 2 weeks to find a block ?

Yes... and we got much more ethers if we find 3 in the following 2 weeks. But nobody knows what will happen the next two weeks. Only that we will reach between 98% - 102% luck/effort within the next 20 blocks is 98% sure...

Edit:

Sorry! If we find every two weeks one block we are 2 days too fast...

If we need two more weeks till our next block... Yes we will earn less than if we found the block earlier...

It depends on how you look at it. The block reward is still the same no matter what, it's not that you are getting less ether for the block, it's just that you are wasting more electricity for it. So you are getting less ethers for Kilowatt/h, or less ethers per a unit of time. It's like this at every pool. Sometimes you find the block faster than the expected time, sometimes it takes longer. At coinfoundry, most blocks are found faster on average and we end up earning more than at other larger pools, where the time to find a block averages out more at 100% expected time. For Ethereum over here at coinfoundry, we are at 67% average, it will go worse a bit now with the due block, but still better than mining at a large pool.

Alright thanks for the info

One more thing: the calculation changes as soon as we gain more hash rate. So add your two extra miner rigs and technically should cut down on each block time by a couple days.