Should be expected from a book like SIA, they are not that quick when they are not backlogged. Would not doubt that a lot of SIA's clientele are pulling their cash out as fast as they can. Wouldn't worry.
I put in a withdrawal request today that had to be processed manually (because my last deposit was not by Neteller) and it hit my Neteller account by late afternoon. I was very pleasantly surprised by SIA's prompt email response to my request and prompt processing of the withdrawal.