How many tunnels each day?

My guess based on Stonecutters precedent is one per day (because there's 19 days left in this phase and 16 tunnels still left, I think the three today thing was due to the wait we had in building the initial things (I don't know if people who donut rushed saw three tunnels when they first started or fewer))

Basically I assume the game creators want to encourage daily play (or more frequent)...one tunnel a day would do that better