I think that with the inevitable slowing down of the difficulty increase rate, the build quality of the miner becomes increasingly important. While first ASIC generations became irrelevant in 4 months, SP30 with 5.5TH will be profitable till 2000PH network. (for 10 cent electricity at current bitcoin price till the next split).

So basically, I think people buying miners today are buying them for a long long time (year+), and should take build quality, support and warranty as primary consideration.