Can you capture and show us your DSL Stats? with the SNR Attenuation and Sync etc... So we can understand what might be a possible reason.
I'm not sure which revision of 5200 you have. But try using the following link to unlock your 5200 to get the stats if they arent showing up already.
»Unlocking your Speedstream 5200 E242
Technically speaking, if your DSL light goes off... it should just resync as soon as line becomes stable. You dont have to reboot your router etc.
I think you have manual connect for the modem. So when it disconnects it doesnt reconnect again. You can change the option after unlocking the modem.
Just when your internet stops working. Ping your router or access another computer over the network so to be sure if the router is working. Alternatively, you can access the modem at »192.168.2.1
and check the status of the internet connection. If it is active or down.
read through the Sympatico FAQ if you need more help with 5200 in the forum links at the top.