The fire button on regulated is always live so it can recognise the 5 clicks on and off. But it does not carry much current - it tells the chip inside when to send power to the 510 but the full current sent to the 510 is sent directly from the board to the 510, it does not go via the tiny microswitch under the fire button.

Imagine a low powered switch that operates a separate high powered switch or a circuit breaker that carries the main current and you won't be far off the mark.

The real reason regulated mods frequently last is many vapers are cheap bastards (myself included) that don't want to pay for quality and look to pay £30 for a mod and expect it to have the same quality of build as a $60 from 3 or 4 years ago. To sell the manufacturers must find ways to sell cheaper - one of these routes is cheaper components.

Look forward to a future of pod mods and shitty disposables. Most vapers would rather buy a shit $30 battery voltage output pod mod and plastic tank every 3 months or an even shittier $5 disposable every day than spend $100+ on a device built with quality components.