Hello and welcome. There is no set growth rate. There are A LOT of factors that determine how fast they grow. Some grow really fast, some really slow. All of them continue to grow as long as they are alive, but growth slows way dow, in most cases, after they reach adult size. Most tortoises will reach full size in around 10 years. Any of the giants would be an exception to this. Sulcatas take closer to 20 years, Galops and Aldabras more like 50-70 years.