According to this lithium batteries last longer if they are not allowed to fully discharge. They don't have a 'memory' like older style batteries.
I always run them down until they stop working though and haven't noticed any problems. I've got one istick that's about 2 years old and one that's over a year old, still getting 3+ days out of both (50W).
Yes they are Polter. And yes the 'lock' is a safety thing to stop them discharging fully. I remember when I was looking at mechanical mods there were lots of safety warnings about not using them past the point when the power starts to tail off or they can overheat. Not a problem with regulated mods.
It's a mod that has circuitry to control how much power the battery puts out. All the variable voltage / wattage and temperature controlled mods are regulated. Ego batteries are regulated too - they put out a constant 3.7 volts and switch off when they don't have enough power left.
Mechanical mods OTOH are basically just empty tubes that you put a battery in and screw a tank to the top. They put out whatever power the battery is capable of: 3.7 volts for most of the time, but a freshly charged battery will put out about 4.2 volts for a short time and when it's running out will tail off to about 3.4.