A 301 doesn’t pass value on a fixed schedule. It passes value as fast as Google re-crawls and reprocesses the two URLs, which is why there is no honest day count to give. The transfer tracks crawl frequency: a well-crawled site sees the destination pick up the old page’s standing sooner, a rarely-crawled one waits longer, and full processing can run from days to many months. Google frames that as a patience threshold rather than a deadline, recommending you keep the redirect in place permanently and at least a year, so its systems see the change enough times to record it.
On the leak half, the old worry that a 301 bleeds a fixed slice of authority is out of date. The current consensus, drawn from Google’s own statements, is that a permanent redirect passes the large majority of signal with little lasting loss, because it works by consolidating the old URL’s signals onto the destination as its canonical rather than leaking them down a pipe. What actually costs you value isn’t the 301 itself. A redirect to an irrelevant page gets read as a soft-404 and passes almost nothing, a chain of hops wastes crawl and weakens the signal, and leaving internal links pointed at the old URL holds the transfer back.
So set the redirect once, keep it permanent, and clean up the things that genuinely leak: send the old URL straight to a relevant destination in a single hop, and update your internal links to point there. Then wait the crawl window out instead of expecting an instant handover, and don’t read a slow first few weeks as value lost.