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).
Don't forget that with more exams, your RHCA level raises, so further challenges will be reflected in your current RHCA .