@jimkbeau The way I see it, failure is just an accurate way to measure your training AND your peogress. If you train to failure for 4 sets each time then you know that is how hard you worked, but if u train for 6 sets without failure then maybe yiuve done 5 sets equivalent or 1 set equivalent.
You can still make progress, but you might be working too hard or not enoigh, maybe u did something wrong out if the gym and youve got no ultimate feedback to tell u that you didnt grow.
My advice, start training to failure. Maybe u want to start low, 1 2 or 3 sets, or jump straight into an intermediate level at 8 or 12 sets.
If you dont grow, its either not enough volume ir a bad diet. In my experience if you are experiencing excessive. Soreness, it is bad diet (can also be seen as excessive workload)