UK Mark,
I am not sure of the question, but I think you want to know if when your spouce is granted a visa to come to your country does she have a time limit to come there by? In Canada I have not heard of a time limit for the spouce to come here, but your spouce has to be in the country 3 years before she can apply for citizenship. If she leaves Canada for a visit back home or leaves the country for a vacation, the time she is out of the country is added on to the 3 years. For an example, lets say that she goes home for a visit each year for 2 months. This would result in a total of 6 months being out of the country over the three years. So she would have to be here 3 years and 6 months before she could apply for citizenship. I do not know if the visa would expire. I have not asked this question yet. A colleague of mine and his wife are going through the process of applying for Canadian citizenship now. This is the Canadian process that he explained to me. I would say just ask the immigration office of your country, or check to see if the information is on their web site, if they have one.
Dave C