Ryan:SSRI Antidepressant ?

Can you take an ssri antidepressant forever or will it eventually not work because of tolerance build up?  Is tolerance even an issue with an ssri?  if you do build a tolerance, then can you only take a ssri until your tolerance builds to the point where you would have to take more than the allowed maximum prescription?  so what are you to do if you need an ssri forever and the amount you need is above what is safely prescribed?  also, if a person takes a ssri for 5 years and they taper off correctly, will their symptoms return and be worse than what they originally had?  i would hate to take an ssri if i knew that eventually it wouldnt work b/c of tolerance issues and then i would be in even worse shape than b4 i started it.  i realize that coming off can be tough.  im not concerned about that part of it.  im concerned about after the withdrawal symptoms subside, will i be worse off than originally.  i know there is no for sure answer but any help would be greatly appreceiated.  it just seems hard to believe that a person could take an ssri from 30yrs old until 85 yrs old or however long they live.