A new plug every 5 oil changes? You're lubing and cleaning the threads with oil every time you screw the drain plug in... it's a bit overkill. I've never changed the plug or the crush washer with no leaks whatsoever.
The 4cyl's have it lucky, steel pan, steel bolt. No dissimilar metals to seize to each other. The V6's with aluminum pans are not so lucky. Combining overtightening with dissimilar metals makes it SUPER easy to pull the threads out with the plug.
Here's the deal with tapping oil pans on the car... you will have no idea if you got all the shavings out. A tiny bit of shavings in the crankcase can go a LONG way towards prematurely wiping out bearings.
Since it sounds like you're going replace the pan, here's some tips:
- Use brake clean and wash down the seam between the pan and block, try to go 1" up from the bottom of the block.
- Use brake clean to wipe off any oil and sludge that my be on the sealing. If Honda uses Hondabond for their gaskets instead of just rubber, pick up a gasket scraper. I said gasket scraper, not a putty knife.
- Make sure you get a "flat pack" gasket. If you buy an aftermarket pan that has the gasket rolled up in a ball, toss it out. Silicone impregnate paper gasket blow, they're know to seep through and known to blow gasket out and leak.
- I'm pretty sure the pans just use RTV silicone for a gasket, if so, pick up a tube of Hondabond or Permatex's "The Right Stuff" gasket maker ($20). It's expensive, but well worth the cost. Lay a solid 3/16" bead around the entire pan, go on the inside of the bolt holes.