So I have a J315 Jacuzzi brand hot tub. A few years ago the display/controls started freaking out, flashing digits and such which I ignored and then the heater failed-just wouldn't heat.

Eventually had the local pool store come out and they replaced the control board which fixed everything.

well guess what, the controls/display are doing the same thing again...All the controls work fine but the digits for temperature flash so you only get 1 digit at a time 1.....0......3......., but everything works fine.

Sound like a control board issue again? Exact same symptoms as before....Real question is, replace the board now or ignore this minor issue and see what happens? (just don't want a repeat of last time when it failed when it was like 5 degrees outside....

Unfortunately it does sound like the same control board issue. If you have the pool/spa store folks come out and fix it, you might ask them if there's anything you can do to prevent this. Maybe there's something about the environment that you could control. I presume you aren't storing any chlorine or acid near this control panel -- those fumes can oxidize metal and is not good for circuit boards (especially soldered connections, or so my PB has told me regarding my gas heater circuit board I had to replace once).