Current session info not cleared after browser restart

As I understand docu for Session parameters, it should be cleared every time I switch off browser (and in few more cases). But it looks, like it's kept forever.

I have application, where you choose area, and data for this area are presented. Then you can choose any location from this area, and application generates more detailed information about this location only.

As this process takes a lot of time, I've decided to store them as session parameters. If they are needed again (eg. to generate chart), I take data from session parameters, do not re-generate them again. And at this point, it works.

But I was using this application yesterday. Closed all browser windows. Switched off computer. 19 hours later or more, I log into TWX - datas are still there. Logout, close browser, open different browser (previously it was edge, so I used Chrome), log into TWX - datas are still there.
Have checked timeout, keeps default value (30 mins).

Is that normal behaviour? Does it depend on some settings (if so - which one)? Can I somehow push to clear this session info from my service(so I could start such service everytime when I open my mashup)? What if start this app at different PC with my user and will not reach moment when data are generated - it will read previous data? Or if use this same PC but log as different user? 

Function used to store info: 
Resources["CurrentSessionInfo"].SetGlobalSessionInfoTableValue({name : "myname", value : resultInfotable});

Function used to read info: 
result = Resources["CurrentSessionInfo"].GetGlobalSessionValues().myname;