was he fearing that overusing his ms will make him go blind and he need replacement sharingans or something else.
Actually, I think he used Kamui in that situation, not Izanagi.was for his izanagi. He can only use it once at a time, but he has a nice stash in between battles. That's how he lived from getting amaterased by sasuke.
that would be one way to look ...and also he planned it way before...he wanted to use them in war ...lik how all those former jin's wielded sharingan ...was he fearing that overusing his ms will make him go blind and he need replacement sharingans or something else.