Basically, Quarterly, the default for *-RELEASE, gets security upgrades, build fixes and fixes for anything stopped working to work again only.
And Quarterly branches from main (aka latest) every quarter (early Jan., Apr., Jul. and Oct.).
Next one (2026Q2) would be branched in early April (soonish).
If you want to use anything new but running supported *-RELEASE, you need to manually switch default pkg repo to latest.
But as it means there could be more breakages on latest, (re-)read Chapter 4 of the handbook, especially Chapter 4.4.2, before trying and decide whether to switch or not.