sooo... 3 things.
you still have all the time in the world to decide what to do each turn.
i've never actually had a problem with the time limit on a mission, its just encouraged me to be a bit more aggressive rather than wait for enemies to come to me. (and normally, its like 'shut down this transmitter by turn 8, and then have as long as you want to kill all the enemies/escape/etc')
there were mods released on day 1 to remove the timer. (though as i say, imo they're ok - they just mean you can't deal with every mission by having all but one of your squad overwatch, whilst you're final member goes forward 5 spaces)