Hello Roi
By default, the holddown timer for EIGRP is 15 seconds, and the hello interval (for Ethernet networks) is set to 5 seconds. If you change the hold-down timer, the hello timer will not change. I suspected this behavior, but I also labbed it up to confirm it.
I assume your question comes from the rule of thumb that says the hold-down timer should be 3 times the hello timer, right? Well, this rule of thumb is not automatically adjusted when you change the timers on EIGRP routers. You must manually change each one individually.
I hope this has been helpful!
Laz