Right now the boot timeout is hardcoded:
private static final int BOOT_COMPLETE_TIMEOUT_MS = 360 * 1000;
Although this is multiplied by 2 in some conditions it is often still not enough for us. Our Jenkins slaves are VM's, with varying performance depending upon the load in the datacenter.
Sometimes our Android vms start within 720 seconds, but more often they don't.

Since I haven't found a workaround I have marked this feature request as Major.