Permanent alimony, in contrast with temporary or rehabilitative alimony, continues indefinitely. The primary reasons that it ends are the death of the payor, the death of the recipient, or the remarriage of the recipient, though cohabitation of the recipient with a member of the opposite sex also is a possible reason for cessation of permanent alimony. The cohabitation needs to be of a permanent or near-permanent nature, with the parties sharing living expenses; a few overnight visits does not constitute cohabitation for the purpose of stopping alimony payments.
Unless there is a specific agreement stating otherwise, payments of permanent alimony can be adjusted upwards or downwards based on a change of circumstances. In the event that the recipient gets a particularly well-paying job or receives a significant amount of money from another source (a will, lottery winnings, a personal injury lawsuit, etc), that might be a basis for reducing alimony payments. Conversely, in the event that the recipient incurs unexpected medical expenses (that are uncovered by insurance), that might be a basis for increasing alimony payments, but only if the spouse paying alimony has the ability to pay more.
A basis for reducing alimony can be a significant drop in income by the payor, such as retirement, though courts may examine the basis for the drop in income. If it is not through the fault of the payor and is in good faith, the court is more likely to approve a reduction in alimony. The reduction will probably not be approved if the drop in income appears to have been created for the purpose of reducing alimony.