@Foofie,
It all depended on the contract or court sentence. And most were sentenced or convicted of stealing a loaf of bread or something similarly banal to feed their starving families, or sometimes they were out right stolen and forced into a life of servitude. Some were for small amounts of time 5-10 years, but many others were there for life, as were their children. Yes, the Irish were the most common convict/slave/indentured servant and not just in the Americas or the Caribbean, in Australia as well. Other poor or orphaned English kids were used and abused too. And many were brought to these places in boats the same sad way African slaves were brought here, in horrible conditions, many died en route as well or whilst working in the same terrible conditions later slaves did.
Ironically, long after slavery ended, this was still the fate of many poor and orphaned kids until or as late as the 1970's in some places. Mind you, I doubt the working conditions were so lethal, then it was the physical and sexual abuses that continued. I recently read an article of how a generation of poor children in Switzerland we're abused in the same way.
I highly doubt many were able to climb the social ladder once they were released, at least if the stayed in the same geographic areas. Although, I was recently watching "Who do you think you are" and Reba McIntyre found out one of her great grandfathers was a slave and once he was released from his 20 year contract, signed at age 11, went on to do very well for himself. Surprisingly, his grandson, then became a slave owner himself. I guess some lessons were not learned, or taken to heart.