How is spousal support calculated in the context of a long-term relationship?

The comparative standards of living of the parties following the breakdown of the marriage are to be considered, with increasing emphasis the longer the marriage. As stated in Moge v. Moge, 1992 CanLII 25 (SCC), [1992] 3 S.C.R. 813, at 870: Although the doctrine of spousal support which focuses on equitable sharing does not guarantee to either party the standard of living enjoyed during the marriage, this standard is far from irrelevant to support entitlement.... As marriage should be regarded as a joint endeavour, the longer the relationship endures, the closer the economic union, the greater will be the presumptive claim to equal standards of living upon its dissolution.