While I really like the SF's balance and handling, I think this is perhaps stretching it a little. In most circumstances where one is expecting to observe for long periods, one instinctively seeks to brace one's elbows, whether against some convenient piece of structure or against your knees when seated - and in that situation most binoculars can be looked through for long periods. If one had to observe from a standing position, completely freehand, with no support available, I think yes, I might be able to keep a SF to my eyes longer than something else, but I'm not sure about much longer.