Stated earlier by Cityhawk:
"If our income exceeds our expenses by too far a margin (a problem we are not likely to have) we will need to make sure we find something related to the club's mission to spend it on (a good problem to have)."
This is easy to remedy in most cases. If structured properly, it simply takes a vote of the BOD to move the excess funds from operating accounts to long term reserves. In some cases those long term reserves have to be specified to the intent of funds, etc, but there is some flexibility.
Also keep in mind that there are many cases where contributions to non profits are not tax deductible, and this varies with structure and intent. As an example, most HOA's are non profit, but the dues can't be deducted on taxes.