Always look at net assets.
Ever heard of the concept of Jaws? It's a measure of success used by management of companies to explain their results. What you want is positive Jaws - the % growth in your revenue should be greater than the % growth in your expenses.
Even if the % growth in your income is the same as the % growth in your expenses, you should be growing in absolute dollar terms.
In order to do this one could argue that you need your asset base to grow faster than your liability base. In some respects it doesn't matter if your debt actually grows, provided your asset base grows faster, AND the ability of your assets to generate an income (rate of return) is also higher than the cost of your debt.
For what its worth, I have over a million in mortgage investment debt, which is being paid off very very slowly. So long as the asset base grows, I know I'm coming out ahead.