So the reasoning is this: there was never a user specified timeout for 2i, and there was a bug in the coverage FSM that meant the timeout (of 60 seconds) was reset every time a results were received from a vnode. When the fsm was fixed, some customers ran into the issue that their 2i queries were failing and they were unable to set the timeout (hence this fix.) The infinity default here means that 2i behaves as much like the broken 2i of old as possible.

I'm not wedded to it, but I'd hate to cause our users trouble over something like having consistent defaults.
We can change it to 60 seconds at 2.0, maybe?