I test and inject 4 times a day, before breakfast, lunch and dinner, and then again before bed when I inject a long lasting insulin.
As for your initial question I’ve more or less stopped the 2 unit squirt... but you should always do it when you start a new pen (maybe even 2 or 3 times) to make sure the needle is primed properly. The other reason to do it would be to check that the needle is working, in 5 years of injecting I’ve had several needles that don’t work, so yes maybe the 2 unit shot is worth while, maybe I’m just getting lazy.