Hi and welcome to ECF. I personally feel that you should vape at whatever wattage satisfies you (even if it's lower than recommended wattage, the only "bad" thing that will happen is that as you say, coils will last longer.) I vape below recommended wattage quite often and still get a satisfying vape (with that said I am locked into high VG due to my PG sensitivity, so I tend to find a satisfying vape at lower wattages with plenty of vapor.
So if you are SATISFIED with your vape, do that. If you are NOT satisfied with the vape, and want to use higher wattage but dissatisfied with your coil life at higher wattages, that's a different issue.
Juice also affects coil life, so avoiding gunking factors (dark, NET, sweet, food coloring added colors) will also extend coil life, so that's an option as well.
If you'd like to vape at lower resistance to save on battery and juice life, then yes, you'd want to find an appropriate resistance coil, that may not require as much wattage to heat.
But really, what you do is entirely up to you and what works for you. I'd agree that lower wattages often will extend coil life, so if your vape is satisfying you I see absolutely no problem.
Anna