Is there such a rule as a tank is too big? I have a 1 HP pump and want a big tank.

Thw answer is the bigger the tank the more water deliveres during drwdown so less cycling. Even better for the pump is a properly sized cycle stop valve or csv

Tom--the answer is that it can be too small, and so your pump cycles more often, which is more wear and tear on the pump and switches.

the larger the tank the less the pump runs between drawdowns, Considering the amount of water the well can deliver between cycles.

I'm not sure if there is a "rule", but in the description section, it says that proper tank sizing is critical to the life of your pump. Therefore, I don't know why the first answer you received from Utilitech themselves would say you can't have a tank too big. It seems to me that they are contradicting themselves.

You can not have a tank which is to big for your pump.