Andrei, there's nothing wrong with a release every 3 months broadly speaking.
But plugin developers need stability: less time means more costs and less income, so are not so encouraged to develop complex solutions. Since they release, they need to upgrade to next release.
Furthermore, for shop administrators and webmasters, release upgrade is a nightmare. Since all plugins have been released and tested, CSS and views have been adjusted, next release is in beta. This means jump 2 - 3 releases, otherwise costs and time spending are exessive.
Now that Nop became really stable and rich of features, time between releases should increase and releases have to introduce really significant and complete modules. Two important releas a year now is perfect.