In your own words:
"my legs are all over the shop as I'm struggling to rack the weight back up....or I have to drop the bar onto my power rack cause I can't get it back up"
That's not "slightly" cheating, that is all out complete concentric failure.
Not advisable to do every set unless you want injuries and to stagnate in your training.
If you want to go to failure, I would use rep speed as a good indicator, once the rep speed diminished significantly but form is still good, terminate the set. The last set of an exercise or the last exercise, sure consider going past that. But overall, staying a rep or two away from training will allow you to train much more consistently.
It makes it much easier to plan progression as Ecko noted above with his example:
week 1 315x7
week 2 315x8 or 317.5x7 or 320x7
James 1:16-17 ESV
Do not be deceived, my beloved brothers. Every good gift and every perfect gift is from above, coming down from the Father of lights
With God's help...Mens sana in corpore sano