Its just a good practice thing. I believe there actually is a hard limit but its enormous. Those warning messages can actually be edited in preferences too. In case you are a repeat offender and tired of looking at the warning text .
As a good practice for us, we try and keep our handlers short and to the point.
We have various models we work with that have close to 260 actions and each action has a handler with a maximum amount of 15-20 lines of coding, unless stated otherwise, to keep the model running smoothly.