Sovereign Default: Definition, Causes, Consequences, and Example

Imagine if you will a government that lived within its means (except in times of war or national crisis. spending shall we say no more than 95% of the revenue it took in the previous year. The remainder invested in safe investments with mild returns on investment. After almost 250 years of contributions accruing compound interest, how long before the government became self-funding. I know that will NEVER happen, but imagine it.