For all the hours I spent in the cockpit, I can't ever remember being bored. There are just so many things that need to be done, overseen and thought about. To even think of entertaining myself with a video or computer game is unthinkable. Hey, but that's me.
So what is there to do? I'll give some examples of the myriad tasks that one can do. First and foremost fly the airplane. That means keep it upright at the desired heading and altitude and free of dangerous conditions such as ice and turbulence. To do the latter requires paying attention to the ever changing weather. That means updating your preflight weather via the radio or using some newer on line technique now available. Part of the problem with the more sophisticated planes is that they can be largely automated. The autopilot takes care of heading, altitude and aids in landing, but it can't think for you. If there is "traffic" at your 12 o'clock and five miles you must be looking out to avoid a midair. That means staying in touch with the ground facility that is watching over you e.g. approach control or center. Another reason to listen to the appropriate radio facility is that there might be an emergency such as a plane in distress that " center " is having trouble hearing and hopefully you can help. That has happened to me. One day center was having trouble communicating with a pilot who was in need of a clearance. I was asked to try and reach the pilot. As I was successful, they had me relay it to the grateful pilot. Made me feel useful and not bored. Also, a conscientious pilot will monitor 121.5, the distress frequency when able. Who knows one day you might be in trouble and need help. There are many examples of airline pilots helping out in cases like this (that is if they are not too busy with nonsense).
Other basic vital tasks include monitoring fuel status. Is there enough aboard to reach the destination with adequate reserve? If flying in IFR conditions is there enough fuel to reach the destination, and if the weather sours and you can't land, fly to the alternate, land with 45 minutes of fuel in reserve?
And so on. Believe me it never gets boring. Especially if you enjoy being up there and take your flying seriously.