From whom shall I learn the Dhamma?

瑜伽師地論 英譯 Yogacara bumi sastra

pg 1262

Because a Buddha enters into paranibbana, one may thus reflect: “From whom shall I learn the Path? From whom shall I learn the Dhamma?” Reflecting thus, one stirs up deep zeal and energy and quickly practise the Path, quickly learns the Dhamma.

If however, there are more than one Buddha arising in a world at the same time, then one may not have the same sense of urgency.