How long does it take to get something live?
Connecting a source and modelling it is usually a day or two. Getting it running cleanly on a messy database takes a few weeks. Those are two different problems and they're worth separating, because people quote the first number and then get surprised by the second.
Connection is quick where the database sits on your own server and your own people administer it. It's slower where it belongs to a software vendor who has to expose it to us, and that clock isn't under our control, which is why we ask about data access before we ask about projects. Modelling on top of it - making the data usable, so a question in your own vocabulary returns the right answer rather than a plausible one - is fast once the data is reachable.
Then the exceptions, which is where the few weeks go. Every real database has them: the field that meant one thing until four years ago, the same supplier recorded three different ways, the inter-branch transfer booked at zero revenue and full cost. None of that is exotic and all of it has to be worked through before the numbers can be trusted. It's the part nobody budgets for.
A first build on top - a report, an extraction pipeline, a reconciliation - runs in parallel and can land inside the same window. Full coverage across every system you have takes considerably longer and depends almost entirely on how many systems there are.
The honest caveat: when we've been late it has been because a vendor was slow to grant access, or because a field meant something nobody had written down. It has almost never been build time.