How long steam key will work?

Yes. Most likely.

Yes , it will :)

yes

steam key will steam the steam key the key the steam key for supreme commander gold edition 24 hours

I'm joking, it lasts as long as Steam lasts unless someone else uses it

3 days

pretty much it will work

As far as I know, keys don't usually expire.

Did you check the best before date?

Yes. (On a side note: wth, how did you get $122 contrib just from bundle games?!)