I'm fairly sure this is by design as an anti-cheat thing. In my experience it seems to take longer to let you back in if you're in an instance and even longer still if you're in battle, although I haven't done any formal testing!

SE have no way to tell actual disconnects from simulated ones (someone pulling out the cable) so they're most likely erring on the side of caution so people don't use it to skip moves/mechanics that would otherwise wipe them.

To OP: If you log into your router, it might (should?) tell you what the expiry time is for your IP address (Check under DHCP). With that you might be able to at least plan when it's going to happen (would have to check before starting game each time). You might also be able to renew the IP address from within your router (starting your 24 hour window again from that point). Failing that, you could just turn the router off/on before you start playing for the day. There's a high probability that'll force the IP address to renew and you'll have 24 hours from that point.

Also you could ask your ISP if it's possible to get a static IP address (currently you have a dynamic one). They may/may not offer this service and may charge a little extra a month for it, but you could ask. If your ISP doesn't change you wouldn't have these issues.

Hope some of this is some help!