I find the 25 turns scenario are usually too short, but i never get that feeling with with the 30-45 turns scenarios.
When i find a 25 turns scenario i would like to play, i now consider manually increasing the lenght in the Scenario Editor.
The problem is that the briefing is very important in a 20-25 turns scenario, and the recon should be done by the briefing. If not, recon is too long for the lenght of the scenario.
In a 30-40 turner, you can afford a proper recon and fight the battle correctly.