The life cycle of major Drupal versions is becoming ever smaller. Whereas Drupal 6 was supported for 8 years and Drupal 7 will be supported for nearly 12 years before it it's EOL in late 2022, Drupal 8 will only be supported until next November, 6 years after it launched. Drupal 9 will only be supported for less than 4 years after it was released, and this pace will probably be the new norm from now onwards.
Until now, we as a community, and agencies offering Drupal solutions to their clients haven't had to really worry about major version upgrades, as most sites were already obsolete by the time that the next major version came along.
We did an excellent job with the Drupal 8 to 9 migration, as most sites able to run on Drupal 8.9 can be upgraded to Drupal 9.1 with only some minor effort required. This is in large part because of the excellent community initiatives to get modules ready for Drupal 9. However, some sites are still blocked in Drupal 8 as they depend on unmaintained modules. As a personal example, in the past few months, I became co-maintainer of many modules just to get them Drupal 9 ready for this reason.
In this session I'll propose how we can alleviate this problem both when building and maintaining their sites, and in supporting the community.
Agencies will need to adapt their existing client relationships to account for 1-2 major version upgrades during the lifetime of a site, and this should be planned from the beginning.
https://www.youtube.com/watch?v=VpXD6lKYFwM&ab_channel=DrupalAssociation