Hi Stuart, thanks for your comment and my apologies for my late response - the Xmas rush of projects at work had my attention.
I'm viewing things with confirmation bias. My bias is based on 20+ years of observation that 99.9999% of 50+ doing strength training exercises, especially in the gym, are wasting their time.
There is a remarkable 0.0001% of those 70 and 80 who perform 2.5X bodyweight deadlifts, and they understand the value of your advice.
My view is that for the others, rather than sitting on a machine for 10 minutes, rushing through a few inconsequential sets with 2 minute rests, and then stumbling as they push themselves to their feet to move to the next machine, that they'd be better off doing something else.
For example, 10 swings of a kettlebell would do them more good than the hour they spend at the moment on the machines. But most people hate kettlebells, so that's not realistic.
As they are not approaching any atrophic benefits, my bias is to move their thinking towards shorter breaks and bodyweight exercises. This is to improve their aerobic engine (stamina) e.g. improvements in mitochondria, capillarisation, myoglobin, size of the heart, strength of slow-twitch fibres, muscle glucose uptake.
The hope is that from this improved conditioning, they could then confidently do more bodyweight exercises, free weights, use standing cable machines, kettlebells and TRX etc. However, in their current state, straight off the machines, they find these types of exercises too tiring and challenging. So a transition path is needed.
Improving their aerobic engine is a very beneficial transition path.
And ultimately, I hope that they may then also feel the motivation to ask how to incorporate more strength training, and be given regimes that suit their age.
For example, a well-constructed Scandinavian study found that 80% of long-rest atrophy benefits from the standard barbell lifts were obtained by a routine of 3 sets of 6 to 8 reps at 60% max with 20 seconds between reps and 2 minutes between sets. This regime dramatically shortens the time required and gives reasonable benefits.
So fundamentally, most oldies in the gym are fooling themselves with extended breaks.
In my view, moving to more of a focus on stamina would give them the foundation to move to a shorter-regime actual strength program. The latter is not a substitute for ultimate strength but a lot better than they currently get from jiggling on the machines.
Meanwhile, for the oldie heavy lifters - may the long breaks be with them.