If they are running solid you might as well keep them since with the other S9/T9 they might get dead boards.
I bought these to heat my home but I am removing all mining gear from my home. The idea is to trade for S9/T9 and have them hosted.
All 16nm Bitmain products are prone to failing boards so pick your poison
You bought mining equipment for the purpose of heating your home... lol. Normally that's the secondary purpose, not the primary one.
I've been looking at the R4s lately and they are interesting. Right now my S9s are stuck in my spareroom, but I want to put some miners in my office, but I don't want my office looking like an industrial warehouse like my spare room filled with S9s and other random gear I've collected over the years...
Where do you live?