Okay, I’ve read the new Community Guidelines banning Adult Content (”human genitalia”, “female presenting nipples”, and “sex acts”).
If you are not affected, or don’t care, great - keep on Tumblring.

But, if the ban on adult content will cause you to become inactive, then you should not let Yahoo/Tumblr count you as a user, for advertising revenue purposes. Deactivate.
Tumblr will flag and transfer your adult content into a sub-account available only to you. This will strip your archive of everything not vanilla, but leave your site to be counted as active so as to keep advertising rates high.

So, it you’re going to be inactive, transfer your content to a new platform if possible, and Deactivate Tumblr.