Is autoclaving sucrose solution necessary?
I wouldn't autoclave this solution - sucrose will partly break down into glucose and fructose. A portion of the sugars will also caramellize and color the solution yellow to brown.

If you need the solution to be sterile, I would filter sterilize it, although this can be hard because of the higher viscosity of the sugar solution. If you haven't seen any negative effects of preparing the solution fresh with autoclaved water, I don't think there is any need to change your protocol.