Not just checking the post activity but should definitely make at least a post every now and then since moderators will mark your account with like resurrect after long inactivity and this should be avoided though.
Posting shouldn't be an issue thou. Some users don't really love to post much but just like browsing through and reading only.
AFAIK, the warning "
This user recently woke up from a long period of inactivity" only happens when one has not logged into the account for a long period and not necessarily because they did not post after long time.
Posting gap becomes an issue only when the user's style changes from the previous posting style after a hiatus and it can actually help assess if the account has been taken over by someone else.