Ds applied for probably 20 or so, but in batches of around 3-4 every 2/3 weeks in order of closing date. He didn't get anywhere with the first batch, but it was useful experience, he learned from the process, and he did things differently for the next batch. Then he started progressing through stages for some of them.
He kept a spreadsheet to control/monitor them, i.e. deadlines for completing each stage, links to copy & paste what he'd written on each application etc., so he could copy & paste the same answers to common questions thus saving time and being consistent, and also links to screenshots, again for reference.
Almost a full time job at times as he was juggling new applications alongside doing the later stages of earlier applications.
He was very busy over Xmas and New Year, including several recorded interview style question/answer sessions.
"Live" online interviews/group sessions were mostly in January/February. He only had one proper face to face interview.
He extensively referred back to what he'd done in earlier rounds of the process for consistency in his answers (as suggested by his Uni careers advisor in case the interviewer tried to confuse him or trip him up).
In the end he got three solid job offers, two where the process had been entirely online and the one face to face interview. He asked to go and look around the two online ones to get a feel for the physical workplace and they were very helpful and arranged a tour with no problem at all, in one it was a HR person who did the tour but in the other it was the dept head himself who'd done the final live online interview, which is the job he took. Accepted it formally around early March.
Even that late, he still got notification from other earlier applications that had gone "dark" so he assumed he'd not got through, but they invited him to next stages which he didn't pursue. So basically for some, the whole process was quick between stages but slow for others. Typically 3-6 months between starting the process and formal acceptance.
Ironically, the job he took had the quickest process - it had the latest application deadline of mid December so he applied early December, did the early stages in later December/early Jan and then online live interviews/sessions in January and offer received early February - no delays or slow progress at all with it.
He's been there 3 months and loves it. Well paid for a starter grad scheme, fantastic prospects etc. He says the guided tour clinched it as he loved the place and the staff were all friendly and welcoming.