README: some edits/additions

README.md

@@ -25,10 +25,12 @@ This documentation is more thorough than for previous versions of this patcher,
 ## Compatibility of various Mac models
 Note that this information is incomplete and may not be 100% correct yet, but I'll add more information over time and fix any errors as I learn about them.
 
-Also, note that on 2011 and earlier Macs, "no graphics acceleration" is a tremendous, almost exponential, slowdown. A simple benchmark, simply minimizing a Safari window, gives the following results (all of these are 13" MacBooks):
-- Late 2012 MacBook Pro: <1 second
-- Early 2011 MacBook Pro: 14 seconds
-- Mid 2009 MacBook: 25 seconds
+Also, note that on 2011 and earlier Macs, "no graphics acceleration" is a tremendous, almost exponential, slowdown. For instance, consider a simple benchmark, simply minimizing a Safari window:
+- Late 2012 13" MacBook Pro: <1 second
+- Early 2011 13" MacBook Pro: 14 seconds
+- Mid 2009 13" MacBook: 25 seconds
+
+Keep in mind, Mojave and Catalina will probably receive security updates until roughly September 2021 and September 2022 respectively (give or take a month), so most users do not need to urgently upgrade to Big Sur.
 
 Mostly compatible Mac models:
 - If you have a 2013 or later Mac, please check [Apple's official list of supported Mac models](https://www.apple.com/macos/big-sur-preview/) (search the page for "See if") first, to make sure that you actually need this patcher.