I wouldn't make a routine habit out of being late. Whether or not SAD's ”matter”, you are still expected to be at work relatively close to on time, and you are still a probie... If you aren't going to be on time, make it a rare event, and for pete's sake don't be like the guy in DEN who is getting a rep for never showing up more than 10 minutes prior to departure without so much as an apology or explanation! All that being said, it is relatively infrequent for a callout to be right at the two hour mark, usually you do have more notice. Be warned, occasionally they cut down your 45 minute prep time to give you the two hours without delaying departure. Honesty with the company and courtesy with your crew is the best policy, never commit to less than the two hour fallout, if you get stuck in traffic let them know, and as others have said, have them patch you through to the captain so they can anticipate and prep the flight.