Tarnicus: No there is a time limit for all forms of the game. As mentioned earlier, there is an "over rate restriction" in the limited over forms of the game (20 and 50) and they have to bowl all overs in the allotted timeframe or the team gets a fine. Game can be interrupted by weather, in particular rain, and then the number of overs are reduced. For example, one team might bowl their 50 over and then it rains. The team batting second might only have 30 overs of batting and the score they need is reduced, using a convoluted mathematical equation that no-one understands lol.
Test matches last for 5 days, and can often end in a draw! Each team gets 2 opportunities to bat. Test matches can be both very exciting and very boring, depending on the result. It is the sort of cricket to leave on in the background whilst doing something else and watch the beginning, the highlights and the end if close.
Okay, thanks for explanation ! (even if for me it's mainly "theory"). I hope to be able to see at least a part of a match one day, to see a little what it looks like :)