Look also at the existence of the 10 demi-brgides of veterans in March 1800 totalising 12500 old soldiers
In 1804 the 10e Demi-brigade was commanded by a colonel of 70 years old - division general Jean Baptiste Vigoureux, Comte Duplessis., having 1103 veterans and 76 officers under his command. The 1st batallion was under the command of division-general Maximilien Stettenhoffen, of Austrian birth, 66 years old, who was already in the French army since 1763.
In 1810 those demi-brigades were transformed into Regiments.
When in revolutionary times, those veternas were used for active duty, as guards of castles, and so on, I wonder what became of them under napoleon.