Leaving it on all the time
If boost is your default setting, it stops feeling like a boost and starts feeling like normal. You pay the extra battery and juice cost without getting the "wow" effect. Save it for when it actually matters.
Using boost with 20mg+ salt nic
The extra wattage vaporizes more nicotine per puff, making high-nic juice harsh and potentially nauseating. Normal mode is the right choice for 20mg and up.
Running boost on a nearly-dead battery
Boost mode draws more current. On a low battery, this can cause voltage drop — the device can't actually deliver the boost wattage, so you get a weak, inconsistent hit and drain the last of your battery faster for no benefit.
Using boost on an old coil
A worn coil already tastes muted. Boost mode will just burn the remaining wick faster and possibly give you a dry hit. If your coil is on its last legs, replace it — don't try to "fix" it with more power.
Assuming boost = better flavor for every juice
Fruit and mint love boost. Custard and tobacco often taste scorched at higher wattages. Test both modes with each new juice — don't just assume boost is always better.
Not trying the middle settings
Many devices have more than two modes — OXVA has ECO / SMART / BOOST, and mods let you dial wattage precisely. You might find that a medium-power mode gives you 80% of the boost feeling with much better efficiency.
