I started doing a slight tweak to my workout routine.

I do 1 set per exercise, and push to do 20 reps of that set. If I don't make it, I rest for 30 seconds and try to squeeze out some more, and repeat until I hit 20 with minimal rest.

I write down the weight and the number of reps of my first failure. When I can make it to 20 reps without failure, then the next workout I up the weight. It works really well, and I can do a full body workout in under 45 minutes and get great gains thanks to really tapping out each muscle group.

Doing heaver weights and less reps tends to cause more injuries for me (I am 46) and I always found I had plenty of gas still in the tank when I did drop sets, so I knew I wasn't really reaching my limit. This makes it so I can reach my limit without having to pull off plates and do lots of sets. It also gives an clear goal - 20 reps every time, even if you have to take mini breaks.

Research has shown that number of reps is not really that important to muscle growth - what is important is pushing to failure, and this seems to really get me to that failure. If I can't even do another rep at what should be a fraction of my 1 rep max, then I know that I have reached true failure.