Welcome to GBO Muscles ... !! I hope you enjoy the site as much as I do. There are many good people here that want to help you with any issues you are having.
As for time at the range, there will be many different points of view because it is something that there is really no "one answer" for. Personally, I shoot 3 shot groups while in the early stages of load development. As I start to zero in on my best load, I start loading 5 rounds for each test load. I always shoot "round robin" when trying to find the load I am after. In other words if I have five different loads I am going to test today for my .223 bb Handi, I will fire two fouling shots (factory ammo) to start. I then fire one round of load #1 at target #1 followed by one round of load #2 at target #2 ... followed by one round of load #3 at target #3 ... and so on. I let the barrel cool down after firing one round of each test load. I try to cool the barrel down to where it was after firing the the two fouling shots which is pretty cool and then I start with firing the second round of load #1 at target #1 ... the second round of load #2 at target #2 ... and keep repeating this method until I have gone through 4 rounds.
This round robin method of test firing helps eliminate a lot of the variables such wind, barrel temp, etc and gives a better view of which loads are the most consistent. I then take the last round of each test load and shoot all of them at target #6 to see where the best consistency is. Here is some good reading and Dan can explain it much better than I. To simply answer your original question, it is much easier to shoot smaller groups with three shots naturally, than with five shot groups but five shots will tell you more. After finding my "best" load, I then challenge myself to shoot the best 3 and 5 shot group I possibly can.
http://www.clik.to/optimalchargeweightbjm