The Brazilian Business or Tourist visa is typically valid for 10 years from the date of issuance, allowing for multiple entries.
The Brazilian Flight Crew (Tripulante Avaio) visa validity can be anywhere between 30 days and 5 years as determined by the Consular Officer processing your application.
The maximum duration of stay per entry is up to 90 days. You may not exceed a total duration of stay of more than 90 days per a year.
Brazilian Visas are issued at the discretion of the Brazilian Government and as such may be issued for lesser validity and or number of entries without explanation.