Mae amserlen y seilwaith dan ystyriaeth hefyd wedi cynyddu o 5 i 30 mlynedd i 5 i 80 mlynedd i ystyried y ffaith y bydd oes llawer o'r seilwaith dan sylw yn rhychwantu llawer mwy na 30 mlynedd.
The timeframe of the infrastructure under consideration has also increased from five to 30 years to five to 80 years to take account of the fact that much of the infrastructure under consideration will have a lifespan of considerably longer than 30 years.