Windows losing IPv6 address after ~10 minutes

When I initially connect to my home network my windows PC is assigned an IPv6 address - however after a few minutes it loses this address! I seem to have similar behaviour on multiple hosts using both wireless and wired connections.

My router is an Asus RT-AC87U.

How could it be losing the IPv6 address? How can I mintor / diagnose this issue?

Update: Based on @grawity's suggestion below I ran wireshark on this. Sure enough I see a Router Solicitation message and a Router Advertisment message with a Router lifetime of 600 seconds. After 600 seconds my computer drops its Ipv6 address.

What is supposed to happen? Should my host send another Router Solicitation message? Or should the router periodically resend the Router Advertisment message?

Update 2:

• RFC 4862 says that Router Adverticement messages should be sent periodically.

Solution 1:

Ok I think I figured this out:

My router has a flag that says Enable Router Advertisement. This was enabled - but by switching it to disabled (restarting) and then back to enabled (and restarting again) seems to have done something to the router and now wireshark shows it sending Router Advertisement messages every few seconds!

Solution 2:

FYI, I have an answer, for those of you that don't have a "RA switch flip", in your router (I use a Cisco RV340 at home, an SMB router), so it's got a bit "more depth" in the IPv6 area. I was really scratching my head over this, our Win10 machines were all losing their IPv6 gateways, at 50 minutes, give or take a few seconds, right after a whole slew of RA messages (monitored using Wireshark). Turns out, it was my Router Lifetime value, which had worked fine, at the default 50 minutes (3000 seconds), for at least 2 years (I suspect my ISP changed something on their side here). Changing to 5 minutes (300 seconds) fixed, this, completely, for 3 different (wired) machines, and one WiFi machine, I tested all of them for several hours, each.
This also greatly reduced the number of advertisement queries, in general, although I'm still not sure I understand why it had that effect (I'm still learning the nuts/bolts of IPv6, at least at-depth, the documentation isn't quite as "well developed" as IPv4, for obvious reasons). Anyway, hopefully this clarifies things, and helps the next users who find this entry.