Nowadays, there are large applications written by groups/teams, which are worked on for three or more decades. For example the ACL2 theorem prover has its roots in the 70s and is used/maintained until today for users in the chip industry.

Common Lisp was especially designed for the development and production use of complex programs. The military at that time wanted to have a single Lisp dialect for those - often applications came with their own Lisp, which made deployment difficult. A standard language for projects was then required.

These were usually developed by teams in the range of 5 - 100 people. Larger teams are rare.