It all depends on the time someone got to spend on learning for the exams, if someone is working 100 % doing the exams can take a long time and be hard.
I would suggest if someone have an another job to take 4 months unpaid leave do 100 % study learning the practical & assessment important stuff and question banking the rest.
Of course it requires self discipline to sit down and work with what you shall do.... I did my ATPL exams from March 2019 to early July 2019 (4 sessions skipped the one in May). It was not especially hard when having good time to work with the exams. Of course everyone is different and learn at a different pace.