I allways switch it up myself. Sometimes I stay 6 nights, but I've also been there for 1 night only. All depends on what you wanna do I guess. Myself, I prefer to stay a bit longer when there's a big chance for good weather.
About the tickets: You need to pick them up at the stadium, starting from 2 hours before the game, but it's well arranged. Make sure you know exactly which sector you buy tickets for though, as the point of pick up depends on that.
For example, if you're in the "tribuna est" you'll have to pick them up at the ticket stands on "Corso Sebastopoli". If you have tickets to for example the Ovest side, it's on the opposite side of the stadium and that's quite a long walk.
After completing your purchase on the Listicket site, I'd advise you to print your confirmation (iirc there something called my purchases on the Listicket site), speeds up the process when you're at the stadium. Just make sure you go the right counter when you're there (prepagati & first letter of the family name of the person who ordered the tickets.)
For your sake, I hope you'll be able to get tickets. Sadly, recent events have made that rather uncertain if you ask me.
If there's anything else you'd like to know: shoot. (I assume you know where you can find both Juve stores

?)