Relationship with doctoral advisor?
I very much doubt any of them &quot;forget&quot; in the sense of &quot;Who are you, and how did you get this number?&quot;
The relationship one has with their former advisor will depend on both the advisor, the graduate, and their relationship - and it will evolve over time. Some are happy to go their separate ways, some continue to be long time collaborators or friends, and the amount of political capital they will spend on their former graduates varies wildly.
Some advisors (wisely IMO) step back a little bit to make sure that their former PhD students develop an independent research agenda and voice, and clearly have a separate career from their advisor.
But it all depends. Personally? I keep in touch with my advisor, see him at conferences (back before COVID-19), and when the opportunity is right, we collaborate, but we don't actively seek out those opportunities.