Would of been better if your lair was inside a dormant volcano, or on the moon, or the centre of the earth. Those are real henchmen locations...
those are rookie henchmen locations...
dormant volcano - still rampant with sulphur fumes, which cloud the mind and cause irrational decision making, hence why bond et al always beat them in the end.
moon - good for hiding, but the logistics costs of maintaining an effective oxygen supply plus the sheer cost to transport any stolen loot removes any proft from the haul
centre of the earth - see moon, but add the motlen boiling lava (which also adds in the added issue from dormant volcano)
see it needs to be in plain sight to be effective - no one suspects what is right in front of them...
eg. you know the accor budget hotel (the old forumle 1) near the M4 in wentworthville? there's a reason you can never book a room in that place......