Well- generally I believe from reading antiminer models have 1-1.5 year lifespan of profitability (making more than the power costs to run it). So as long as you can pay back your purchase in a few months, or at least less than 10 -11 months (time it takes to get money back on GPU) I say go for it.
Hope to get your $ back on it and HODL for a purchase on the NEW model...
I just bought 2 D3s. I am fairly confident I will get them paid back in 1-2 months then its gravy... But we all KNOW these are all gambles... But it is FUN. The banks are ripping the world off every day and they are all propped up by the governments so they cant fail.... I want any little bit of insulation from them as I can get.