100% rinsing Xenoblade Chronicles 3 for every last piece of content it's got to offer is going to take you significantly longer than if you just breeze through the story. As things currently stand we're now 180 hours into our playthrough and we still have a few bits and pieces to mop up. Again, we've been super-methodical in playing through for guides and a ton of screenshots, so without the need to worry about these things we reckon you're looking at 150-160 hours.
If you check out our guide to 100% completion, you'll get a better picture of what's involved here, with Unique Monsters - of which there are a whopping 140 - taking a good long while to find and kill. Unlocking every class for every party member and completing some lengthy late-game quests will also take you quite a long time so settle in and get a brew on if you're looking to find everything this one's got to offer.