You're both right. Some tortoises experience a growth cessation and live for a long time afterwards, while some continue to add (at the progressively slower pace) growth little by little till fairly near the end. This doesn't seem species-specific so much as it seems specimen-specific. Growth halting seems very common in some "turtle" lineages.
The meat of this sandwich is that, as we all know, every species of tortoise slows significantly at some point after maturity is attained. Once this stage of life is achieved, growth progresses slowly enough such that pyramiding should not prove much of an issue.
Pyramiding is related to an over/underabundance of certain factors that cause improper assimilation/formation of the units that build the shell (calcium crystals, etc.). The slower that building process is, the less noticable pyramiding will be. So, once the given animal's number one metabolic goal is no longer to get "big" quick, you see less and less of a trend towards pyramiding. This is why the greatest damage can be (and frequently is) done in the very early years.