Does SSRI drugs treat depression forever? or someone must them lifetime?

chrisatmudd gave you a wonderful answer. Meds are temporary and they last as long as you take them which is why people are told to take them as perscribed and inform you doctor if you make changes or stop taking them.

Therapy and meds is the best treatment for depression along with excersise and a healthy diet. Excersise alone can improve depression up to 50% because it releases neurotransmitters in the brain called dopamine which are resopnsible for our happy feelings. Therapy and meds can teach you how to manage depression and work through symptoms.

My understanding is that its effect is temporary and that you'd have to use them for life, but that the hope is that SSRIs coupled with psychological therapy can reduce the need for SSRIs to the point where you wouldn't need them anymore.
I was told that you don't need meds for depression....that you need to jump around and praise the lord.
:]mhm mhm.

To answer your question: I have no clue.
SSRI drugs artificially raise the available serotonin levels in your brain. Once you stop taking them (that is, if you can get over the addiction), your brain is going to have the same problems it had before you started, only worse because it got used to the excess serotonin and it is lower than it was initially. Also, too much serotonin means your other brain chemicals become dysfunctional, so you have depression with other problems.
two years ago I was having anxiety attacks and had a bout of depression. I started on Cymbalta and it worked great for me.

Then I started having, what I thought, was some depression symptoms but it turned out it was signs of being over medicated. At the suggestion of my doctor I started to ween off the Cymbalta and I just took my last pill about a week ago. So far so good. So I would say that you are on them as long as you need to be but it is very important to report any changes in mood to your doctor.