Besides the overall durability and precision build, there are two other things about the SB and BB that set them apart.
First is NO gaping slots or holes for venting. The vents are located behind the switch, out of the way of debris. The switch is designed to shift in the event of internal pressure, exposing the vents. Judging by the pictures of a SB that had two batteries melt down inside of it, this system works as intended. Meahwhile, there are no worries about dirt, spilled beer or pocket lint getting inside.
The switch is not fully mechanical. But it is a commercial grade, vandal resistant switch of the type used on public intercom systems and ATM machines. It's rated for 1 million mechanical and 200,000 electrical cycles. Before it's installed, it's modified to increase those cycles to an estimated 400-600,000 electrical cycles. I have estimated that I have put well over 250,000 cycles on my BB and it has never once misfired. I notice no difference between how it feels now as when it was new. If it ever needs to be replaced, the cost would be minimal in terms of labor and it would definitely be worth the expense. Meanwhile, it has taken zero maintenance, unless you count the time I sprayed some stuff in there after dunking it in the Gulf.
In fact, all the maintenance I have ever done was lube the threads and, about every 6 months, polish the positive battery contact with a pencil eraser.