How much screen time should be allowed per day on mobile phone for 2-5 yr olds?

I allow mine who is 5 to use but limit maybe 30 mins or 45 mins per session and he gets 1-2 sessions per day Always emphasise the distance between eyes and screen The brightness on screen etc etc I personally feel that they do get to learn quite a bit on educational apps and eye hand coordination. Basically everything has to be done in moderation. If restrict, later when they grow up... they will want it more or get addicted because they feel that they are deprived from it Educate the disadvantages and advantages rather than forbidding them Teach them rather than disallowing is my point of view