Is standing up and pedaling on multi-gear bicycles a bad idea After reading  While pedaling standing up, bike crank gives in as if shifting, what is causing this? , I was thinking "one should probably not be standing up to pedal under normal circumstances". Is this an accurate assumption? 

I remain seated while pedaling but I am not sure if it's right, or how to justify why one should not stand, other than it may be unsafe due to unpredictability in the drive train. 

Instead I shift gears to make the bicycle easier to pedal so that I can remain seated at all times. 

Should we remain seated at almost all times when on a multi-gear cycle? Why?
As (almost) always, the great Sheldon Brown has covered this particular topic. Standing while Cycling


  To Sit or to Stand?
  
  It is my belief that a great many cyclists stand up to pedal much more often than they should. I've often said:
  
  "If you find yourself standing to accelerate, on level ground, it is a sign that your gear is too high or that your saddle is too low."
  Standing pedaling allows you to apply more force to the pedals than is possible seated, because you can rest your entire weight on the driven pedal, and, even more, by pulling up on the handlebar, you can push the pedal with more than your actual weight...but is this a good thing?
  Pedaling that hard is very stressful to the joints, and to the bicycle, and usually involves a level of effort that cannot be sustained aerobically. Unless you have unusually good form, it also tends to involve a fair amount of thrashing from side to side, which is a waste of energy. The added stress flexes many parts of the bicycle, and the energy required to do this flexing is not usually recovered when the parts straighten back out.
  
  These extreme stresses also greatly increase the risk of breaking things. If a pedal, crank, chain, handlebar or handlebar stem should break under this abnormal stress (a very real possibility) you are almost certain to suffer injury in the resulting crash. Even a simple missed shift or the skipping of a worn chain can toss you to the ground when you throw all of your weight onto a single pedal. You should never stand up to pedal a bicycle that you do not know to be in excellent mechanical condition!