It has been a lot of hard work, but totally worth it. It took me 6 months with some breaks in between.
I used RHLS as my main study resource with 180 hours of lab time utilised. Exams taken:
I found Puppet to be the hardest exam of them all. Ansible was a new thing to me, but all other topics are more or less what I do at work.
[EDIT: May 2020]
I've also passed OpenShift (EX280) and Hybrid Cloud (EX220).
Technically the criteria for RHCA elligibility is to have RHCE + 5 contributing certifications active at any point in time; now note that many of the certification content assumes you have an RHCE-level knowledge. While nothing prevents taking the 'advanced' certifications first, it might make more sense to take RHCSA+RHCE first, the others later.
Also, any passed certification contributing to RHCA will extend your RHCE expiration date, so that maybe easies your path :-)