I have always built up any nicks etc with a stick welder, and then laid on a couple of beads of hardfacing material, and then used either my 8" or 4 1/2" angle grinder to grind a new cutting edge. You will be ahead if you try and keep as much blade as possible, and continuous sharpening does nothing but take away parent material to get a new edge. Building them up and grinding it to form and then hardfacing may take an extra hour or two, but the end results will be well worth it. If you lay the beads on a little at a time, and allow to cool a bit between passes, and don't get the blade super hot, it will not affect the baldes material at all. There is a myriad of materials available in welding supply shops that will cover a vast array of applications. You can get high impact low abrasion, high impact high abrasion, etc etc. Some rods are work hardening, so as they are used it gets harder and harder up to a certain pre-engineered hardness. Personally I would remove the blades from their attach point clean em up a bit, a nd hardface em and then finish sharpen them. A dealer is not going to tell you this as they need to sell replacement blades, but I have been hardfacing mower and bush hog and other items for over 25 years and have never had the first problem. I just made a replacement knife blade for a blade in my Agrifab chipper shredder vac cart. A new blade was over $25 plus shipping. I used a piece of blade from an old mower blade, cut and shaped it to size, and then built up the edge with stellite hardface rod. Ground a bevel cutting edge, and installed it and gasve it a work out. At the time I replaced this chipper knife, I also built up my flail knives on the shredder sectin of the vac cart. I used stellite rod there also. Just the oter day when I installed my new hose and deck adapter on the agri fab I checked the flail and chipper knives and they showed no signs of wear, just nice and shiney material, and the chipper knife had as good or better of an edge than the one original remaining chipper knife I sharpened and resinstalled. My blades on the bush hog I have are pretty darn sharp for a bush hog blade and its been many years since they were done. I used to redo all my JD 180 blades like this as well. especially the high lift blades, in the web area where the blade makes it upsweep to form a lifting foil. They used to wear and erode very quicky in that area and make like a pronged fork on the ends. After a hardface built up they seemed top last just about forever. Yes it will take a bit longer to grind a new edge, but you will be happy with the results in the end. Normally most hardface rods require at least 2 passes. The second pass helps eliminate any inferior material contained inthe initial pass and makes for a higher concentration of precipitates of carbide or whatever the material is in the rod that makes it hard. Usually no more than 3 or so passes is needed, as too much takes away from parent metal strength, but the process is all alid out in the welding rods literature or from the dealer in the welding supply house. An angle grinder or belt type grinder is best to sharpen them with IMHO. I normally always use an abrasive disk anymore over a stone as they seem to cut better and last long and just produces a better edge, but a strone will work on an angle grinder as well.
Check the mount holes in the blades for any signs of cracks or elongation or egg shaping of the holes, and also the mount bolts. Any cracks in the blade or if its showing signs of being egg shaped, you may want to replace the blades. If bolts are grooved and worn replace them too. If you have access to a mill or large drill press and the holes are nmot too badly egg shaped so that you still have lots of parent material left around the hole its possible to make and insert bushing in them. I have done lots of blades for folks around here over the years. Yes, some blades are cheap to buy but over the years it adds up, so I make a set of blades last a very long time. I have added zerks to the pivots on my hog. It uses 1 1/8" diam bolts to attach, which are Grade 8 bolts. I drilled these bolts with a passage way for grease and tapped the head for a zerk. Now a quick and easy shot of grease every now and then cut back on the wear on these items. The drilled passage ways for grease did not harm the bolts integrity at all.