I've only reinforced once, when using Jowel yarn that comes with reinforcing thread. I did both toes and heels.
I'd have to say for me it is more likely the heel turn/bottom of the foot and the ball of my foot more likely to wear on socks.
I've read you need to be careful what you use to reinforce - some fibers will put more wear and actually tear/cut thru the sock yarn then help strengthen/reinforce it.
Mirl56 at Ravelry, too.
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Lady Feb Sweater
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