Rules as written, the number of journal entries is random. If you were extremely unlucky, you might draw two jokers back to back from the get-go and end up with a four-entry game. That would be unfortunate, frankly, since your character has more chances to develop over a longer game.
On the flip side, you might end up with a joker on the very bottom of your deck and end up writing more than 54 entries!
You can control how long your game is by stacking the deck. Shuffle your standard 52, then draw as many entries as you care to write with the cards face down. Slip one joker somewhere in the middle of that, and another onto the bottom.