Re: Wife going to pak, how long can she legally stay away?
I assume she is here on a two year spouse settlement visa? Theoretically she can stay away for as long as she likes, the visa won't expire simply because of how much time she spends in either pak or the UK. The only to bear in mind is when she comes to apply for indefinite leave to remain that they will probably question any prolonged periods of time spent outside the UK during the two years and simply reissue her with another two year spouse visa again instead.
I suppose their point of view is that if you're not spending that much time in the UK then you don't want or need UK residency.