LED resistor values?

[Jidis]

I was talking to Thorsten in another thread about a misbehaving light on an MB64. I got to wondering if there are any consequences to minor (or extreme) differences in the current limiting values for the lights. I know the digit displays running the low value 220 ohms are actually being scanned, so they're not constantly on.

Without getting into trying to calculate an Ohm's law total current value and comparing it to the max capacity of the core supply or the 595 chip's limits, can you safely go up or down a range (say 150-1k) without affecting (or destroying) your average MB circuits? By average, I'm talking probably one full D.Out, but maybe two. Also, I'm guessing you can mix and match values, from one output to another, for different amounts of light on different indicators?

Again, I'm only looking for an estimated guess on the "average" setup (standard LED specs), and not only the obvious power supply and heat issue, but any affect any of that could have on the function of the shift registers.

                                                  Thanks!

George

PS- Also, if you think there's an ideal version of the 595 for heavy or weird loads, that would help too.