The normal guidance for "when are ribs done" basically consists of tugging at ribs a bit and seeing if they want to release. I've really never liked this and think it yields a slightly overcooked rib. I don't want to overtoast the Espresso BBQ Rub coating, as well.
My Platonic ideal pork back rib is where it is starting to release but the whole rib will not release cleanly from the meat. Back rib meat is more prone to overcooking than a spare rib, where the rib tug method makes more sense.
I also do not advocate wrapping ribs in foil for this recipe. The rub creates a wonderful toasty crust when applied liberally and cooked at exactly 225 degrees. The cook is gentle enough to not make wrapping unnecessary and it would soften the bark on the ribs.