The longer is the war the higher is the risk for the local population on occupied territories. Not only because of filtration and direct oppression by security forces, but also because of reduced access to healthcare and basic necessities like food, heating, drinking water etc. The winter is coming and the infrastructure in many cities and villages is completely destroyed. Russia does not demonstrate any intent to rebuild it in next few months.

EDIT: „the longer is occupation..“ will be more correct. This is an incentive for liberation more than for negotiation.