So if I've used it and it has 175/255 I can restore it back to 255 with the fortification powder? That would be very cool since I payed like 1.25 mil for this sword.
If it has 175/255, you should use it for a while yet first.
Once it's at, say, 20/255, buy a Blacksmith Repair Deed. They're cheap. Go into a blacksmith shop and use that. Your sword will now be at 254/254. Use it until it's down to 10-20/254, then use another blacksmith repair deed. The sword will then be at 253/253. Etc.
When the second number gets low (say ???/100), you can then use Powder of Fortification to increase it back up to where it was.