HowLongToBeat.com is a site that aggregates gameplay time required to complete the video game of you choosing. Just so you know you can complete it over the weekend, or allot appropriate time to finish it. There is nothing more annoying then getting into a game and realizing you can't finish it in the days to come.
The site is nice enough to break down time to console type, completion type (as in speed run, completionist, main story only) and other sections based on you game. So before you sit down to play a game check with HowLongToBeat just so you know you can complete your game in your due free time.