For me it always depends on how many nodes I initially let the plant grow too, for example 2 main nodes equals 4 side branches. But let me backup for a minute because how many times I top depends on how much space I have because if I only have a 3 x 3 space, I know I should only top those 4 side branches 2 times because with just those 2 toppings I would end up with 16 main tops, which will turn into 22 to 28 tops with good lighting and 6 weeks of vegging and it doesn't ever stop there because when flowering really kicks in that 3 x 3 space will fill-in rather quickly...