How long does it usually take for GOG to update a game to new version.
I have some games on Steam and can see that there is one update and DLC out for one of the games I own on GOG.
Would be nice to know how long it takes GOG to update.

We would wish to know too.
Unfortunately, it goes from just days, to Eternity™.

wholly dependant on the developer and publisher
when they give gog a new update and when gog is done testing it

gog isnt like steam where it all happens automatically
most of us download the games via downloader or browser

there is galaxy which is automated but its been in beta for 2 years now

It varies.
gOg can't promise it will take just 1 day to update, after the devs send them the new files.
Because unlike Steam, they test the game.

Probably a day or two to take the build the publisher gives them, put the GOG special sauce on it, test it, resolve issues, retest, and get it into the final packaging for Galaxy and the standalone installers. That process unfortunately does not start happening until the publishers actually bother to send GOG the updates in the first place however. Sadly, there are more publishers than there should be who just don't give the slightest shit about GOG and turn up here to sell their game, then take months/years to give GOG patches if ever.

The shocking thing is that these games still remain being sold in the store, which is somewhat troublesome because there's no easy way for customers to know if the game they buy will actually get updates at all from the publisher let alone when it'll happen.

Fortunately the list of games isn't terribly large, and there is a thread in the forums that tracks it. Search for "second class citizens".

Don't think that GOG doesn't approach the publishers though - they do, and they're told a song and a dance and never given patches for those games that are outdated.

Van Helsing Final Cut took quite a bit of time. In fairness, GOG supposedly tests each game/update before releasing it. Whether that contributes to the delay, or if other sites do the testing, I do not know.

Postal 2's mega update took about a year to get here. RWS is pretty irresponsible even if they do seem to be nice folks overall. Their best plans are great and all, but their execution followthrough blows goats.

Then there's the Postal 2 mega update that still isn't here, more than a year later.

Woah that's insane!

We got the Postal 2 mega update, but what we haven't gotten is the new Paradise Lost expansion pack nor Postal Redux, which I've concluded at this point are just not going to happen despite what RWS has or continues to claim. They just don't have the manpower and organization to pull it off, and they're already working on porting some freebie expansion pack thing for Steam. Steam gets the entire focus and GOG is less than dirt.

I know. I just posted in that thread ;-)

Yup, they sure do...

I'm just repeating what they said.
Not my fault if they lied!