Spiral inserts! Well if you have a planer and jointer and can not or choose not to go the spiral route I vote for sharpening. Always made more sense to me and on my machines it was always more economical. Especially if you can sharpen your own.
Last time I bought them I think my 15" planer knives made with WKW HSS bar stock were in the $65 range, and sharpening was $.40/inch, or around $18, and the jointer knife cost was a similar ratio. For me it definitely makes more sense to send out the planer knives, I could probably grind the jointer knives my self, but time is short in my world, and I prefer wood working to metal working, so until I get much broker than I am right now I will continue to send the jointer knives out too. If I were a little less broke I would throw a Byrd head in the jointer and spend a little less time setting knives altogether.
Most of the machines at work are terminus quick change heads, and that sure makes things easy, though I'm told that ease of use comes at a cost. CHEAP is not one of the words I have heard used to describe terminus knives, and I haven't found them to out last regular straight knives. I think ours can be sharpened at least once, and they are two sided, but I don't know they would save you any money long run depending on how you value your time?
do mine all the time, I have the Delta sharpening system but a lot of times I just run them on a honing stone
Sharpen mine with the old and trusty Makita horizontal waterstones.
Bill
On the other hand, I still have five fingers.