Thanks to all readers (32) who voted.
The poll shows without any doubt that a playing time from 1.5 to 3 hours is what the readers of this blog prefer (68%).
15% can play up to 4 hours and just 12% more than that.
1 voter have very limited time (1 hour).
Therefore, for my Large Battle game I think we are exactly on target (2,5 to 3 hours).
I am happy about this also because I launched a thread on TMP asking more or less the same question. It came out that many players (mostly American) have few opportunities to play, but when they do they prefer to play for 4-5 hours and they have space enough also to leave a battle for a following session.
Any comments are welcome...