IMO 3-speeds aren't hugely useful, the steps between the gears are too big. They're more like having having three SS bikes all rolled into one rather than an actually geared bike.
I've used a Sachs/SRAM 5-speed IGH that I was rather happy with. 5 or above seems like a good choice to me.
On anything recent, durability isn't much of an issue. With a very minor maintenance effort, they'll go for years. IMO, about the only way of thrashing them while JRA is if you insist on riding them out of adjustment.