As long as it all works out in the end.
That means you can do pretty much whatever you like in the middle of an adventure. If it all works out, cool! If it doesn't, then the GM probably wasn't going to let you succeed anyway!*
* Note: May not actually be the case in games other than Call of Cthulhu, Paranoia, Warhammer Fantasy Roleplay, Warhammer 40,000 Roleplay, World of Darkness, Ravenloft, Planescape, GURPS Horror, GURPS Cthulhupunk, Delta Green, Conspiracy X, ...
Uh, actually it might just always be true.
Obi-Wan: Remember, a Jedi can feel the midi-chlorians flowing through him.
Luke: You mean they control your actions?
Obi-Wan: Partially. But they also obey your commands.
Han: I've been around, and believe me: hokey nanobiology and weapons you can buy in a bar are no match for a good blaster at your side, kid.
Luke: You don't trust the Force, do you?
Han: Sure I do. Blasters are just a lot easier to trade than midi-chlorians.
R2-D2: Didn't you turn the Sand People into rampaging Barbarians by trading them blasters?
C-3PO: And trading midi-chlorians led to... Anakin.
R2-D2: Who ended up wiping out half the Sand People.
Han: So it all worked out in the end, right?