Well, personally I take the exact opposite approach - that is:
lvl 5 weapon - try for +6 in a row (use all my HS if I succeed)
I've done 2 41+10 bows in a row this way with only 4 fails, all of them that did nothing. Other time was a 41+8 which I risked after getting a lvl 5 weapon to +5 in one go then having it die from the +6 - result was, 2 fails - nothing and nothing - and rest were successful.
But if you fail 3x in a row with HS - STOP USING THEM IMMEDIATELY! chances are you will continue to fail.
As for pet armor/weapons, I've never tried it so wouldn't know.
However, I do agree with the part where unique equipment should not be allowed to fail - considering their cost and level of difficulty to obtain...