The SDs are very impressive machines, but I think the machine you're talking about might be the older ED model? I don't know about the older ED, but if it's an early SD and you can get it at a good price then I don't think you can go far wrong, they print beautifully over a wide range of stock.
There will be less trained engineers around than for a Komori or a Heidi, so I'd make sure that you have a press & an electrical engineer within a reasonable distance before signing on the bottom line.
I don't really know about longevity, but I've seen some real old Saks still working at printers and they seem to have a loyal customer base, so must be doing something right. You could ask Sakurai US for references from customers with "high mileage" machines. I would!