Running zmstat-chart to help figure out an IMAP failure (support case 00051719), I got

Code:
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
        at java.lang.Integer.valueOf(Integer.java:625)
        at com.zimbra.perf.chart.ChartUtil.createJFReeChart(ChartUtil.java:1082)
        at com.zimbra.perf.chart.ChartUtil.doit(ChartUtil.java:348)
        at com.zimbra.perf.chart.ChartUtil.main(ChartUtil.java:308)
Apparent fix: zmlocalconfig -e zimbra_zmjava_options='-Xmx448m' (default is 256m)

Has anyone else ever seen this?

I have plenty of RAM, and lots of LUNs and processes that might explain larger-than-usual charts, but zmstat-chart was working on the same hardware with the same configuration last month. Why would more RAM be needed?

Are there other reasons to want to, or not to want to, give zmjava helper processes more than the default 256m?