As an International player - and that is really the only way you earn a decent living:
If you are good - you can last 15-20 years.
If you are average, maybe about 5-10 years
If you are mediocre - maybe a few series before being discarded.
The fear of injury, falling out of favour, not having the right contacts etc - all can contribute to you seeing out your career as a has-been.
Given the level of competition in the sub-continent, I do wonder why anyone would knowingly choose Cricket as a career?