Once you have sample units in hand, put them through their paces. Here's what matters in practice:

• Battery life: Run a full charge and see how long it lasts under normal use. A device that dies by midday fails the all-day user.
• Draw quality: Does it feel tight or airy? Match the draw style to your target user—MTL for ex-smokers, DTL for cloud chasers.
• Leak resistance: Toss a few in a bag or pocket to simulate travel. Leaks are a top complaint and a fast way to lose customer trust.
• Ease of use: Test the filling and charging process. If it's fiddly, beginners will struggle.
• Consistency: Take several puffs in a row. Does the flavor and vapor stay steady? Inconsistency signals poor QC.

Take notes on each device. Compare them side by side against your use-case checklist. Don't rely on spec sheets alone—real-world performance is what your customers will remember.