LEDE Reboot 17.01.2: "Raising SIGUSR1" frequent system log messages

Hi! I have LEDE running on my TP-Link TL-WDR4300 v1 router. Looking at the system log, I see messages like the following. Is this normal? I'd like to fix any problem rather than just suppressing the log messages, which I think I'm able to do. Thanks for any help!

Tue Jul 18 19:57:38 2017 daemon.info odhcpd[779]: Raising SIGUSR1 due to address change on eth0.2
Tue Jul 18 19:57:38 2017 daemon.info odhcpd[779]: Raising SIGUSR1 due to address change on br-lan
Tue Jul 18 19:57:39 2017 daemon.info odhcpd[779]: Using a RA lifetime of 1800 seconds on br-lan
Tue Jul 18 19:59:43 2017 daemon.info odhcpd[779]: Raising SIGUSR1 due to address change on eth0.2
Tue Jul 18 19:59:43 2017 daemon.info odhcpd[779]: Raising SIGUSR1 due to address change on br-lan
Tue Jul 18 19:59:44 2017 daemon.info odhcpd[779]: Using a RA lifetime of 1800 seconds on br-lan

I have now tried LEDE Reboot SNAPSHOT r4675-e5e6045 and the issue with "Raising SIGUSR1" still exists.

As the syslog trace indicates this is an informational trace which is usefull for trouble shooting purposes and is normal behavior.
You can suppress the syslog tracing generated by odhcpd by setting loglevel to 0 in the odhcpd dhcp uci section.

Well, this message occurs every 2-3 minutes. Still normal? Should there be an "address change" so often?

Yes that's normal as it indicates an IP address parameter change; eg this could be lifetime update of an IPv6 address

I see. Not sure why an address would have such a short lifetime and how associated devices keep track of this jumping around. Is there a way to change this lifetime?

Have the exact same behaviour here with the exact same router and running 17.01.4. Although it is informational it doesn't really look normal get these messages so often. Also the lifetime shouldn't be that short.

In the other hand another router (same model) running Chaos Calmer 15.05.1 doesn't show up these messages.

One difference between the first and the second router is that the first one is a DHCP and DHCPv6 Client on WAN port while the second runs PPPoE on the WAN port and then DHCPv6 on the top of it.

Should the behaviour be different like this in these two types situations ?