Are you being fr? Look , it is a fact obito has over 100 sharingan eyes, look at the manga and anime episode of obito trying to take Danzos eye, secondly, it was not plot that madara implanted kamui in his eye that fast , obito gave kakashi his eye and kakashi had it in very short time, the only time it has been shown to take long to "Recover" is when sasuke was receiving itachis eyes for Ems, I went over this, it is very practical, and as far as obito getting damaged trying y access his dimension -_- this was only the case due to konan having several billion explosive tags surrounding obito everywhere while he was " intangible" , against hashimara. He can easily slip through the ground and across the plain of their battle then go to his dimension to access the eyes , then quickly go back to the battle Feild as he is shown to be. Dry fast while using kamui to travel to different locations