[swift] Rolling upgrade, any version relationships?

Hi, we are looking at upgrading our 2.7.0 Swift cluster. In the past I've modeled this on a dev system by upgrading storage nodes one by one (using 2.17 as the target version). This seemed to work well - I deliberately left the cluster half upgraded for an extended period to test for any cross version weirdness (didn't see any). However I'm wanting to check that I have not missed something important. So my questions are: - If upgrading from 2.7.0 is it safe to just grab the latest version (e.g 2.23)? - If not is there a preferred version to jump to first? - Is it ok for the upgrade to take extended time (e.g weeks) and therefore be running with some new and some old storage nodes for that time? regards Mark