Scorpion life spans range depending on the care that is provided. Some people "power feed" their scorpions in captivity, which makes them grow faster. But, it was proven(by someone forget where I found it) that it also makes them smaller as adults and not live as long.
There are some scorpions that only live 2-3 years, but they naturally mature quick and can have multiple broods from one breeding.
Other scorpions can live much longer, but they naturally mature slowly, and take longer to give birth ect.
So to answer your question, you'd need more info. What species of scorpion ect.
In all honesty, I don't know jack about most Buthidae scorpions. I haven't even owned a Parabuthus sp. long enough to have an idea about them. If you want to learn about Parabuthus sp, you need to get ahold of Peter P. He goes by the screen name "Skywalker." I don't know if he comes onto AB though, he's on venomlist.com/forum a lot though.
I dont know exactly how long Parabuthus spp live but I can tell you it takes over 1 year to 2 years for them to mature. One of my female P transvaalicus molted into an adult in late Summer of 2005 and just had her 2nd batch of young and I expect her to have 1 more at least.
You really need to narrow down Buthidae more as like Mike said some only live about 2 years (T falconensis is a shing example) while some will live much longer
the lifespan depends a lot on the genus. A lot of Buthidae spp are fast-reproducing, fast-growing and relatively short-living. On the other side the Buthidae Zabius fuscus for example is really slowly growing. I´ve got cb from 3/`05 and most of them are still 5. instar and far from being adult.
I kept a wc female P. transvaalicus which had been imported in subadult stadium in 1999. She matured the same year and died last year in my possession. Assuming it should have taken her at least 2 years to reach the subadult stadium in the wild, she should have been at least 9 years old at the time of her death. This is pretty old for a buthid scorpion.