How long does it take to get an expired domain indexed after rebuilding? Looking for your real-world experience

Hey everyone,
I'd like to hear from people who actually do this regularly, not the generic "it depends" answers.
Here's my situation: I buy an expired/dropped domain that had a clean history and decent backlinks, then I build a completely new site on it (different niche/content from what the domain used to host). After that, I set up GSC, submit the sitemap, and wait.
My question is simple: from the moment you finish building your new site on an expired domain, how long does it typically take Google to index it?
A few specific things I'm trying to understand from your experience:

1. Does an aged/expired domain actually get indexed faster than a brand new domain, or is that a myth? In my tests it doesn't feel much faster.
2. When you change the niche completely (e.g. old site was a shop, new site is something else), does Google take longer to re-evaluate and index? Has anyone measured this?
3. What actually moved the needle for you — GSC manual request, backlinks, internal links, traffic? Or just time?
4. For those who've done dozens of these: what's your average time-to-index? Days? Weeks? Is there a typical range?

I keep reading "1 to several weeks" everywhere but I want to hear actual numbers from people who've done this many times, not blog post estimates.
For context, I host these separately (not pointed at my main site), build content tied loosely to the domain's history where possible, and build links independently. Still feels slow.
Appreciate any real data points. Thanks.

How good is that domain? What are its metrics? Does it have any traffic?

clean expireds usually get first pages indexed in 2 to 7 days for me. full crawl takes longer. biggest delay comes from hard niche changes. matching old topic even loosely speeds things up. gsc helps a bit but good crawl paths matter more.

what I have learned through my experiences, some expired domains get indexed within a few days while others can take several weeks.

usually 3-7 days for me if niche stays close to history, full niche flip can drag to 2-3 weeks easily