As a mage, +3 is probably a fair stopping point, maybe +5 if you really want the higher end equipment. You need the upgrades for your staff.
For other classes, it depends. As a huntress, I’ll often stop at +11 or +13, depending on what level I found it at. Farming consumables and higher end equipment can be super fun! A +13 ring of wealth will provide +7 armor and weapons, which can easily be game winners. The higher level also will provide several scrolls of transmutation that I often use after dwarf king to get the ring that I want.
While there are some really cool things coming (spatial video, action button, etc), the only reason to recommend an upgrade this year is for Apple Intelligence features. If your phone is old and it’s just your time to upgrade, then it’s a great year for it. But if you’ve got a newer phone, don’t rush for the upgrade.