What advantages are there to painting the inside of the block?

I use 2 different products, I use glyptal as allready mentioned above, and I sometimes use a product from cerakote called "microslick" both accomplish simular results, sealing the pores of the iron, and providing a slicker surface for oil return. HOWEVER, the main reason I use them, is because most of these engines are "hobby" engines that spend lots of time sitting, and I like the corrosion resistance aspect of them. As noted previously, the blocks must be clean. I will only do it after running the blocks through my ampro cleaning system, which bakes the blocks at high temp, followed by shot blasting with stainless steel shot. No other method of cleaning is good enough to coat the inside of the block.