Upgrading to higher major version directly or via small steps?

[c0re]

Hello all!


I'm interested in 2 updates:
- from 6.2 to 7.3
and
- from 6.2 to 8.1

Can I update directly from 6.2 to 7.3? like set RELENG_7_3 in supfile
and make csup. Or I should update to 6.4, then to 7.0, and then to
7.3?

And same question about upgrading from 6.2 to 8.1 - can i csup
directly to 8.1? If not - why is it so?

Thanks!