No. The impact you had by purchasing emission allowances and holding them over time is lasting: the investments made by the compliance entities, the emissions avoided, and the financing of public climate policies continue to have effects. Of course, the longer the holding period, the greater this effect.
Furthermore, each year, the European Commission adjusts the number of newly issued allowances based on the total number of allowances already in circulation (TNAC). By holding emission allowances, you increase the TNAC, and decrease the number of allowances issued on the market. This contributes to reducing the overall budget. For this effect to materialize, the allowances must be held for at least one year.