I used a vpn almost all the time and my line stayed up pretty much 100%.this year when I moved, I transferred CC to my new place and I continue to run a vpn. I now notice, for some reason, that after a few hours, I get a loss of ping to anything. if I stop my vpn, the default router is still unpingable. what 'fixes' it is to reboot the cable modem (and my access pfsense router, which then gets a new dhcp primary addr) and then things are good again for a few hours. not sure if this is related, but if I don't use a vpn, the line stays up for days and weeks at a time. when I use a vpn, I get a few hours at a time.
Check your hardware, including your pfsense and cablemodem.
I'm on Comcast, and I run three VPNs over my residential connection -- SSL outbound from an internal NAT client to my work network for about 8 hours a day, plus a nailed-up outbound IPSEC tunnel to my personal server in Chicago, and I also have a listener for inbound OpenVPN sessions. All this and I've been doing about 100GB/month in torrents, yet my connection is rock solid.