The advice I'd follow in iReviews' iOS 27 pre-update video is the rule the channel abandons in its final minute. Its usual line on big releases is to wait two or three days for public feedback. This time, citing the release candidate's speed and its best Geekbench 6 scores on the device (it doesn't read them out), it says install the moment iOS 27 lands on Monday, September 14.
Storage is the real prep. The channel budgets about 10 GB for the download and another 10 GB to install, and its iPhone Storage screen puts Apple Intelligence at just over 17 GB against about 16 GB for iOS, a gap the channel states flatly.
Apple Intelligence now takes more space than iOS itself.
If space is tight and you never touch those features, iReviews suggests switching Apple Intelligence off. Those features need an iPhone 15 Pro or newer, while iOS 27 runs on everything iOS 26 did, back to the iPhone 11 and the second-generation SE.
The channel expects battery drain for the first few days. A Settings banner reading Optimizing Siri and Search indexes the phone in the background, and the banner itself says longer charging sessions speed things up. On the channel's iPhone it ran for almost two weeks after beta 1, though iOS 26.6 started the same job early for anyone who installed it. Past that, the channel's battery screens show 66 percent of a charge stretching over 8 hours 24 minutes.
One release candidate on one iPhone says little about the public build on an iPhone 11, so midweek is soon enough for me. iPhoners who wait give up a few days with Siri AI, which has kept people waiting far longer than that.
