calculating alimony/spousal support

[mammamia]

Can someone explain to me what factors are taken into account when determining alimony? I have been supporting my family, by myself, for the last 5 years. My husband is capable of working he just hasn't (can't decide what work he should do). If/when we divorce after 20 years of marriage, should I expect to pay him alimony, too? I've been working 2 jobs (60-72 hours per week) to support everyone. Will the amount be based on that income? If I cut back my hours now, before we divorce, would that make the amount smaller? I'm afraid that when I leave, every penny I earn will still be going to him. I don't mind paying child support at all but the thought of supporting him for the rest of my life really grates on my nerves. There's absolutely no reason he can't work...he just won't. I'm just trying to prepare myself for what might come and would appreciate any insight into this matter.