Male and female lifespan
Male Grammostola grossa are generally expected to live roughly 4–6 years, while females can live 20 years or more. The difference becomes most obvious after maturity.
If you buy a Guarani Giant as an older juvenile or adult, you may never know its exact age. Use the species range as a guide and keep your own dates from the point you acquire the spider.
Why females live longer
Female Grammostola grossa continue moulting after maturity, which allows them to remain healthy adult spiders for many years.
A male Guarani Giant eventually reaches an ultimate moult. After that point his remaining lifespan is usually much shorter than that of an adult female.
Growth and maturity
Guarani Giants are slow growers. Young spiders normally moult more often than large juveniles and adults, but the time taken to mature varies between individuals.
Do not try to estimate the exact age of Grammostola grossa from size alone. Feeding, temperature, sex and genetics all influence growth.
Feeding and temperature
A practical temperature range for Grammostola grossa is 19–25°C. Stable care and sensible feeding are more useful than trying to force rapid growth.
Keeping a Guarani Giant very heavily fed does not guarantee a longer life. Fresh water, suitable food, normal moults and stable enclosure conditions matter more.
Mature males
After the ultimate moult, a male Grammostola grossa may become more active around the enclosure and may eat less often than before maturity.
That change can be normal for a mature male Guarani Giant. Keep water available, continue offering food occasionally and make sure the enclosure remains secure.
Keeping records
Record moult dates for Grammostola grossa and keep suitable exuviae if you want to confirm sex. If the spider was not bought as a tiny sling, record the date acquired and approximate size instead of guessing an exact age.
Over time, those notes make the lifespan of a Guarani Giant easier to put into context and help show when growth and feeding patterns change.