Over 3 years of observation in Canada (sorry wrong country ), 212x was my most used power on the moon with 8" aperture, my Newtonian can take it easily. I can go up to 286x (35.75x per inches) occasionally (moon) too but it's never has good has 212x and the image is much darker too.
For stars and DSO it's variable, powers are usually in this range, 29x, 40, 55x, 80x, 143x. The longest time passed at the eyepiece would be at 212x sketching the moon 26.5x per inches of aperture. For the planets, they are very low this year so 212x is not very optimal.. I bet it's going to be 143x, 166x (or less) in 2018 for the Mars opposition this summer.
I am not very tempted to invest in more power then around 200x.. but my telescope could probably handle a bit more on the moon.. (220x, 230x ?) It's not a very good instrument for the double stars so the range between 250x and 400x is not really useful for me.