Hey guys,

i live in a country with a super low electricity cost about 0.004 USD/kwh so electricity cost is not important for me, considering this i am thinking of buying about 10 units of M3s to start mining mainly because of its low price ( i can buy 10 units for 1,600 USD) , but i have one big concern which is the old technology of this miner,  i would like to know if i can use this hardware for like 15 to 24 months? as per my calculations its ROI would be about 272 days with increasing hash rate difficulty of 7% per month, considering this do you recommend my plan, i would appreciate if you could challenge me or give me your advice/solutions.

also i have a warehouse to install them so noise is not an issue for me.

needles to say that i am a noob in mining.  
thank you in advance.