Ask HN: Should I get a new cable modem?

Recently my cable internet service was automatically "upgraded" from 30 Mbps to 300 Mbps (along with an increase in price).

I measured the speed both before and after the upgrade date, and the speed didn't change - around 20 Mbps down and 10 Mbps up (here's a speedtest: https://www.speedtest.net/result/15769158888).

Also my ISP sent out a technician because they detected a problem. The tech didn't see any issues, so he replaced the outside cable (it gets chewed on by squirrels). While he was here, he recommended I get a new cable modem.

Should I get a new modem?

Here are my current details:

ARRIS SURFboard SB6141 8x4 DOCSIS 3.0 Cable Modem https://www.amazon.com/gp/product/B00AJHDZSI/ which I've had since February 2016.

Linksys AC1200 Wi-Fi router https://www.amazon.com/gp/product/B00JZWQTKO/ which I've had since July 2017.

My main computer is connected to the router via Ethernet, and Windows networking settings says the speed to the router is 100 Mbps.

My work laptop is connected to the router via WiFi, and Windows networking settings says the speed (Receive/Transmit) to the router is 585/866 (also in Mbps).

My ISP is Spectrum, and I live in a suburb in SW Ohio (Dayton area).