Like you mentioned, the reasoning behind doing 302 redirects initially is in case the redirect has been set incorrectly, giving you time to check them before Google re-crawls and updates the index. As 302 redirects are temporary, after setting the redirect the old page will usually stay in Google's index indefinitely.
However I do many 301 redirects every week and I have never taken this approach; I simply set the 301 redirect, then check everything is correct straight after. If you have hundreds of redirects to do you can check them more efficiently using the Screaming Frog web crawler. You can import your list of pages that should have been redirected in a txt file, then Screaming frog will crawl them telling you what response code they are sending and where they are redirecting too.
Even if you set an incorrect 301 redirect, it can takes weeks to months before Google updates the index, so you shouldn't really need to worry about sending the 'juice' to the incorrect page; although I suppose it depends on how long until you check if you have done those redirects correctly!
There could also be adverse issues. Say you were doing a site migration and you 302 redirected every URL on your site to other URLs, I don't know how Google would react to that, but it could be rather bad!
As the saying goes 'Measure Twice, Cut Once'!