Yes, it would be best to prioritize updating your website’s core code to include the new G-XXXXX code; this is because Google plans to sunset the Universal Analytics (the UA-XXXX you’re referring to) and it’s being replaced by Google Analytics 4 (GA4). Even though your UA data is still flowing to GA4 for now, it’s not clear how long this support will last; hence updating to the new GA4 property ID is advisable. As per the transition, there’s no rush as Google also offers dual tracking to use both GA4 and UA till you fully migrate. It would be ideal to make this transition gradually and get accustomed to the new interface and data model of GA4.