Marvin gets updates very frequently (~ every two weeks these days). See our changelog for all the updates.
Since Marvin is a very complex app with lots of options, there are many edge cases that produce bugs and issues which are not possible for us to always catch despite testing.
That is why we rely on users to report any issues when a new version goes live.
The desktop apps take longer for us to build and is also more extensive for the user to update.
In the web app you just have to reload the page to get the latest version. In the app you have to download the entire new app, and restart Marvin.
That is why we first release the new version on the web app and wait for any bug/crash reports. Then fix any issues that were caught and then build the desktop apps once we are fairly confident any major issues are resolved.
Depending on the issues this takes about 1-3 days. So you can generally expect the desktop app to come 1-3 days after the release on the web app.