This is an interesting question.
I find that my amount of personal "thinking time" seems to depend on how long my opponent takes to place their tiles. If I'm playing a relatively fast player I usually respond just as quickly (often to my detriment) whereas those who like to take a bit more time to consider their options will usually inspire me to do the same. It often depends on how close the scores are too. If I'm in a losing position and don't consider there to be enough tiles left to recover I can tend to lose heart, and don't always close the gap by as much as I might be able to if a win seems like an impossibility.
A typical time for a basic game (2-players) is around 30 - 40 minutes with that time being evenly split between players. My last game in the Abbey & Mayor league took almost exactly an hour although some were considerably shorter (my game against berchio for example took around 25 minutes I think) and others can be longer.
It isn't uncommon for a weekly game to take as long as 2 hours to play but these are usually between 3 or 4 players and typically include at least two large expansions and a mini or two.
So, in summary I'd say it depends on 3 things:
1) Type of player
2) Number of players
3) Number of tiles
Those are my thoughts anyway.