Answer:
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
Of these things - I have two. One for me - and one for you. And when you ask about the price I simply smile and nod twice.
If a man carried my burden, he would break his back. I am not big but leave silver in my tracks. What am I?
Some try to hide some try to cheat. But time will show we always will meet. Try as you might to guess my name. I promise you'll know when you I do claim.
My first is in some but not in all. My second is in tiny but not in tall. My third in little but no in big. My fourth in port but not in pig. My whole is made in nature's way. For clothing rugs used every day.
No matter how little or how much you use me, you change me every month.