I think the next few days will be a major decision point.
Again, if I remember my pay periods right, the current pay period ends tomorrow, so fed employees are still technically unaffected (pay-wise) as everything is the same as if there wasn't a shutdown. Pay wouldn't be distributed normally until like next Thursday or Friday. If the shutdown ends by Monday or Tuesday, there's still enough time for OPM to process timesheets and get everyone paid on time.
If the shutdown goes beyond Tuesday, that's when the time will start that employees will not be getting paid, at least until the shutdown is over. While many APS members may be saying "so what?", within the gov, I think that will be a point where the R's will want to start compromising more to end the shutdown, because they're going to start being afraid of political backlash.
Right now, with this kind of partial shutdown, it's pretty unnoticeable and no one has yet been really affected (other than people like Jamis - non-furloughed essential employees who might be having to put in extra hours, etc.). Once the dems can actually start proving (versus just saying, as they have been now) that "people are being hurt", that's when the R's will start to waffle because of optics and will want Trump to hurry up and compromise. JMO.