LL may not care about the $300,000 in the bank but the state or feds may find that excessive for a charitable non-profit of your size.
There is no law or statute regulating how much money a 501©3 corporation can carry over from year to year. Also has no bearing on the size of your organization. As long as you file your taxes properly, you are allowed by law to carry over any surplus from year to year. I believe it is form 990. Many NPO's carry over millions of dollars from year to year.
It's a common myth that people believe that NPO's can't make a profit, or must spend all of their money. You can't pay shareholders, but you are allowed to make money and hold it in reserve. There are restrictions on how to spend the money, but you can make as much as you want.
Many NPO's will take a few years to raise money for a specific reason. A good BOD will have those situations all planned out.
NPO's can get backlash from their members if they are raising too much money and not spending it, or not having a plan to spend it. But that in it of itself, does not concern the IRS.