Are gains from training permanent?

[Programmer]

Hello,
I am doing a research on my own whether doing this type of training is worth it.
My biggest concern is that I will lose my gains after I stop playing it. I can't see me playing it after more than one year, so I hope that the effect of it would remain long term. 
Can anyone share his experience, or some research for this concern? 

[Leonardo]

They are not. 

[dominic lambert]

They become semi-permanent the longer you play. It's also easier to regain gains & much easier to maintain gains than it is to get them the first time 

[Veronika Yakovenko]

 Some studies suggest that the benefits may persist (at least) for months.

That being said, it would be unrealistic for anyone to expect a rise in intelligence from a short cognitive training program to be permanent. After all, the effects of even the most powerful fitness program will eventually wear off if one stops working out entirely. By implication, you’ll likely need to keep completing n-back sessions on a regular basis in order to maintain the hard-earned cognitive gains from dual n-back in the long term.