Spousal maintenance is only awarded in certain circumstances and the length of the marriage is largely irrelevant.
A couple could have been married for 30 years or more without one being entitled to maintenance.
It is normally awarded if one cannot adequately support themselves. An example would be where the wife has not worked because the husband has earned a good living and it suited them better for the wife to stay at home, raising the children and looking after the home and husband. After 30 years, she cannot realistically get in to the job market.
Another good example is where one is a very high earner, and tey have both enjoyed a very good standard of living. Even after a relatively short marriage the other could be entitled to maintenance - think of Paul McCartney and Heather Mills.
Each case is different. If each was earning a similar amount then spousal maintenance would not be payable.