An application can accumulate features without limit so long as those features fall under the continuous inspection of automated for-purpose functional tests.
Three times in my life I have undertaken substantial projects with functional tests integrated tightly with the work in progress. The third has come together in the last week.
Automated Testing where WyCash features were bond calculations and reporting mechanisms.
Swim where Eclipse Portal features were long-running transactions with multiple participants.
Wiki Functional Tests were Federated Wiki's second generation was born within pages of situated tests.