Only really useful if you take advantages of the synthetic properties. That includes low temperature flow, high temp resistance, and the biggest one as you alluded to - extended oil drain intervals.
If you plan on doing oil changes every 5K miles - its pretty much overkill with synthetic. Myself, I usually push it out to 10K mile oil changes, because of how much driving a I do - but I also back that with routine UOA or Used Oil Analysis. Since every car is different - some like to run longer oil changes, some definitely can not.
The factory service manual doesn't forbid extended oil change intervals - but it doesn't endorse it either. Also have to keep in mind that oil tech is constantly evolving - oil back when the car was designed (~ 5-7 years before that generation came out) is significantly advanced since then. Even conventional oils in the newest API category could give older API synthetics a run for the money.
Note that you can try it out and see what happens - experiment with it. The old issue of not being able to switch back and forth between them was due to very specific basestocks back in the 70's and 80's. The newest API - you could even mix them and make your own synthetic blend. Each car is unique - some engines like one brand/viscosity over others.
Note that some may post oils that are thicker / thinner - but may be referring to if the oil shears up or shears down as it being run. Example: An oil that shears up - may start as a 5W-30 but after 10K miles be closer to a 10W-40 or even higher - my experience, lots of Pennzoil and Amsoil due this. Some shear down - starts in grade - 5W-30 but thins out at the end, be a 5w-20 or less. This is pretty common with Mobil 1 in the 5w-20 to 10w-30 grades - surprisingly, the 0w-20, 30, 40 grades seem to do the opposite - actually stays in grade of get a little thicker, almost acts like Mobil's Delvac HDEO line.
Example - my 1ZZ-FE Corolla likes thinner oils - Valvoline Synpower and Mobil 1 run great - but something that thickens over time, like some Pennzoil or Amsoil variants - car hates it (MPG drops over the course of the oil run). But something like my previous 2ZZ-GE Matrix XRS - it actually liked heavier oils - even run a 15W-40 weight, as it liked having higher oil pressures, thicker films. Some, like my current 2AZ-FE Matrix XRS - responds much better to a HDEO (Heavy Duty Engine Oil) - something like Rotella Synthetic - actually helped stop some of the oil consumption it had when I first bought it used. Now it only consumes a couple of oz over a 7K-8K mile oil interval. Also seems to like heavier oils, but seems to do better on Rotolla then say a Pennzoil in the same viscosity. The RAV4s are like my Corolla - they like thinner oils, ones that shear down - like Mobil 1.