In Hindu Marriage Act, there are two types of maintenance (alimony). Interim maintenance and permanent maintenance. The first one is only during the pendency of a case under Hindu Marriage Act, i.e., divorce case etc. Once case is decided, the application for permanent maintenance will be filed and disposed off. It will be till she goes for second marriage.
In addition to above or in alternative to above, a wife can file maintenance under Section 125 Cr.P.C. also. There also interim maintenance can be awarded by the court during the pendency of the main petition.
That under Section 18 of the Hindu Adoption and Maintenance Act, a wife can seek maintenance and it will be given till she is "chaste".
The wife can get any or all of the above said maintenance, but while the court grants a maintenance in any particular case, it will consider whether any mainteance was granted earlier under any other law and that would be adjusted in the latter order.
It wlll be generally monthly allowance so that she can sustain.