Tracking vacancy rates and maintenance costs

[Asher Anthes]

So, I have 4 rentals and I compiled my totals for the last 3 years and I had 1.9% average vacancy rate.  My maintenance costs (including cap x) totaled 8.6% of revenue.

I know my vacancy rate is a bit lower than average, do you think my maintenance and cap x is about in line?  I'm wondering if these are realistic numbers to project for the next properties I buy.   Is maintenance as a percentage of revenue the best way to estimate, or do you guys look at it a different way ($ per square foot per year, $ per property per year?).

And I've been able to achieve 2% vacancy mostly by hustling my butt off on turnover, but that also may be a little low for a long term estimate?