How long should one stay in the same job?

it depends, few people stay in company for a long time because of the faith, trust and emotional attachment.
few stay for the long time due to the comfort in the job.
The Ultimate goal of doing a job is earning money and Career growth as well.
Till the time you are getting the opportunity to grow in any of this or both you can stay.
Once there is a saturation its better to think about the next assignment.
ALL THE BEST!!!!!!!

I think that from 3 to 5 years is long enough to stay at the same job