There are cases where people run extended amounts of times on anadrol and halotestin but these are for severe wasting away diseases - or in the case of halo testosterone deficiencies (rarely prescribed).
I'd have to imagine that if primo worked so well for a year round steroid that it might be accepted in the US as a TRT drug, but I'm not sure.
Either way, it'd be stupid to suppress natural testosterone with something other than testosterone because like I said earlier - testosterone has many functions in the body, artificial derivatives will not satisfy them all.