

If I recall the mission timer was maybe an issue only once. I found in my play through on the 2nd highest difficult I had had plenty of time to get into position at low risk and then engage on favorable terms. You can do this to quickly advance forward towards the objective without worrying about finding cover which reduces the distance you can advance. Then move the first solider as far forward as you can with your second movement but make sure he's in cover, if an enemy is sighted on screen, move all your soldiers to the best cover possible, if no enemy is sighted, stack up your soldiers behind the first and don't worry about cover as you won't be attacked even if found.

Knowing this you can advance one solider to max range of his first movement, if no enemy is found move up the other soldiers. However if they are not visible at the start of their turn and then go on screen and discover you, they won't attack you the same turn but instead run for cover. If the enemy is visible on screen and your still in the undiscovered phase, if they discover you they get to attack you on the same turn. With X-Com 2 I found once I knew how to handle the opening moves the timer no longer became an issue. In X-Com Enemy UnKown by far the most effective tactic was to sit back in cover with overwatch enabled and let the enemy come to you which they would do in the vast majority of cases, this slowed the pace of a game and made it less tactical when one tactic was all you needed 95% of the time. Believe the developers went for this option to counter overly defensive play. The mission time limits in X-Com 2 where very decisive among the players.
