Anton Chizhov 

I just spoke to the LC dev team and there is a way to reduce the batch sizes, as opposed to the timeout setting, which will hopefully address this for you.  The  capability will be in the documentation for the descriptor on Monday.  One of the dev team will reply to this post when  it's done and explain what you need to do.

Hi Anton Chizhov,

The timeout can not be manipulated, but you can change the segment batch size that is sent, to your extension, for translation. The default is 200 segments. If you can't translate all of them within 2min, choose a number that you feel confident can be translated within the allocated time. 

To change the batch size, in the descriptor set extensions -> configuration -> segmentBatchSize RWS Language Cloud Extensibility Documentation (sdl.com)

Word of caution: There are multiple layers involved each with it's own timeout. If it takes too much to translate the whole document, a higher level might timeout.