Upgrading to the latest Magento should be advisable always, but I am wrong person to give any advices there. Nor was it the point. I was merely pointing out that upgrading HelloMix theme from v2.5 to v3 is pointless as according to Win Merge program none of the files have been edited (= no changes). Which is fine, you made sure that the theme is working with magento 1.5 and it’s officially supported now. Thanks for that.