How Long Is It Safely Recommended To Stay On The

How long is it safely recommended to stay on the drug fluoxetine for depression.?
I seem to have been on it for several years now. I was weaned off it last summer and put back on it because my depression came back. Are any long term detramental effects?
Should I still be on it after 3 years? I don't seem to be able to get this information or advice form my doctor.