I used to be fairly slack about cleaning dies. So long as they'd work and weren't scratching the brass, I'd use them. I'd stop and clean a die when it no longer worked as it should. For example, when loading cast bullets, an accumulation of dried lube in the bullet seating die might be needed mid process.
When I downsized a few years ago, I cleaned redundant dies in order to sell them. It was then that I discovered just how dirty they can be while not appearing externally to be so. It's especially important to keep the sizing die clean to minimize scratching of the case.
Another issue is, I use RCBS water soluble sizing lube. Which so far as I know doesn't have any rust inhibiting qualities. So if I don't anticipate using the sizing die any time in the near future, I clean it out with lacquer thinner and shoot a bit of cheap, Walmart spray lube into the die shell. I also clean off the sizing button. The spray lube is light, leaves a film but not anything viscous that would attract much dust. Before I use the sizing die again, I spray the cavity out and wipe it down with long stem Q tips.
One more thing, it's a good idea to clean new dies out before using them. I've noticed that new dies sometimes have residual dirty machine oil inside them. I use lacquer thinner for this job.
When I downsized a few years ago, I cleaned redundant dies in order to sell them. It was then that I discovered just how dirty they can be while not appearing externally to be so. It's especially important to keep the sizing die clean to minimize scratching of the case.
Another issue is, I use RCBS water soluble sizing lube. Which so far as I know doesn't have any rust inhibiting qualities. So if I don't anticipate using the sizing die any time in the near future, I clean it out with lacquer thinner and shoot a bit of cheap, Walmart spray lube into the die shell. I also clean off the sizing button. The spray lube is light, leaves a film but not anything viscous that would attract much dust. Before I use the sizing die again, I spray the cavity out and wipe it down with long stem Q tips.
One more thing, it's a good idea to clean new dies out before using them. I've noticed that new dies sometimes have residual dirty machine oil inside them. I use lacquer thinner for this job.