You can do it everyday if you like and don't encounter any negative effects.
Not eating after 8pm I think is a bit relative; what's most important with this type of IF is the length of the eating window. I forget if it's 6 or 8 hours (I do 6 or less), but basically you have a window of time where eating is allowed, and outside of the window you do not eat with the exception of bulletproof coffee. For example, if your eating window is 8 hours and you eat your first meal at 12pm, you should be done eating by 8pm.
The minimum recommended time for a fast is usually 16 hours with an 8 hour window, but I and other people go with a smaller window for potential hormonal and fat loss effects. There are tons of posts and literature on the topic that convey the many benefits.
If you know you will be done eating around 9pm, then you shouldn't be eating anything until 1pm. If you can go a little longer without food you may have increased benefits, but YMMV.
If you get brave enough you could try fasting until your evening meal once or twice a week. You can take some MCT Oil or even some butter in the afternoon to keep your energy up and stay satiated. Do what feels comfortable though and don't be afraid to experiment.
And a warning if you plan to use MCT Oil... ease yourself into it. 1 serving per day at first, then move to 1.5, then 2. Taking too much can result in some undesirable and quite unpleasant bathroom time.