Afraid not, that is my point: every single workout I still feel fine and whatever Garmin measures (resting HR, overnight HRV recovery) is still ok but motivation is gone if I don’t limit myself during Z2 workouts over long periods
EDIT: I think we talk from slightly different angles:
Through my own experience I’ve found that using HRM keeps me from overheating in Florida summer. My problem (especially when running where there isn’t the level of cooling) is that heat exhaustion comes on rapidly (a feeling of nausea) and stays there for a while. Using an HRM I’m able to prevent that from happening. My study has been ongoing for 32 years and found to be effective in this regard. I’m publishing it right here. 
Same here in Northern California. Did some 30 second intervals last night in 100F / 38C air temps and capped the “endurance” at heart rates that I know will avoid feeling like crap the next day. Looking back, power was 120W for awhile and then 90W for awhile to bring HR back down. Hot riding for 102 minutes total last night. Feel great this morning. Learned those lessons 7 years ago.
And no, I tend to ride too hard on RPE and find it easier and better to look at HR every couple of minutes.
My point was use all the tools in toolbox, HR, Power RPE, none make the others redundant IMO.
Each has their use case.
Re Heat and RPE, might be personal to me, but power RPE that doesn’t in many circumstances work for me HR is almost always the first indicator in extreme heat, by the time RPE catches up trouble is close to follow, and power (cycling) are pace (in running) is going to dramatically drop. I’m mainly talking about training, but dependant on what the type of event is it might be important. Having said that RPE works perfectly well if there are no external factors that are different to those I’ve recently been training or racing in.
Timely discussion; just got back to the UK this afternoon where it is 16 - 18 degrees from Spain where it was 30 to 34 degrees, the first 3 or so days in Spain I used HR to dial in RPE which lagged significantly. The last few days I could just base training on RPE, final session it was feeling normal, and I could have used Power or Pace (slight negative offset compared with being back home in the UK, much cooler.)
For me excessive stress, that is going to impact performance is almost always is picked up by HR first, RPE second and finally Power, for others I can see that for other that might be, RPE, HR, Power. I honestly don’t think its power, and then the other two.
To be clear I was saying Power alone doesn’t replace HR and RPE
I never look at HR in a road race, or for that matter power, then you can either hang or can’t (there are exceptions)
Long Story short like I said us all the tools, RPE, HR Power and work out what works for you, so in answer to the post I believe there absolutely is a use case for HR
I’m another one who lives in extreme heat and has learned the hard way that HR signals long before RPE does. Going by RPE, I’ll feel fine almost right up to the moment when everything goes to absolute hell. If I keep an eye on HR, I can back off and keep the crash from happening.
Calling out that it’s mostly in heat where this is valuable is key, at least for me. In the winter, RPE is a much better signal…again, for me.
For me heat exhaustion comes on rapidly without warning - scary rapid. Body says “you’re stopping this sh_t right now!” and gives me a feeling of nausea that stays a while. If it wasn’t so rapid, I could use RPE to keep it at bay, but I don’t want to be put in “time out” so I use the HRM to keep me well clear of that condition. Another thing about RPE. Let’s not pretend RPE is always “truthful” of the stress your body is experiencing. What happens when a surge of adrenaline pumps through your veins so you can fight that saber tooth, or impress that potential reproduction mate?
^ This is absolutely my experience as well, glad I’m not a one off weirdo.
You are not.
Point of order: he could be. Just not for this reason.
Carry on.
But you don’t need HR to hold yourself back - just target a lower power during and/or perceived exertion during and after.
PPP: If you know your power, then at best heart rate is redundant, but at worst it is misleading.
PPP: If it feels hard, it is hard.
Piss poor planning?
Puff puff pass?
Paycheck protection program?
Public private partnership?
Pithy Power Proverb
Thank you sir!
RPE changes w/ my psychological state (depression/anxiety - high RPE, excitement/competitiveness - low RPE). How many times have you seen race cyclists get in a wreck and immediately get back on the bike - only to get off minutes later w/ broken bones, etc. How reliable was the RPE system then? Ever wonder why football players get them selves “pumped up/excited” before a play?
By using HR cap as balancing point, power itself becomes moving target:
For me personally, RPE is actually the worst ruler: Z3+ are pretty spot on but below that I would end up around 70% of FTP (and it feels good). But I know from experience that with my volume this is not sustainable in long term.
Good point. I’ve been off the bike for about a week (sore knee) and today I went on a easy Z2 ride in Florida heat. My heart rate was significantly higher. Was this due to aerobic detraining in a week? Of course not - it was from loss of heat adaptation. Living in Florida I notice this a lot. I expect to be back to normal in 1/2 weeks.
That’s true, where I live, weather is much more tolerable, nice steady 20-25C dry temperature i.e. I can trust more HR not changing too much due external factors.
Very good point, I hadn’t thought about that. 
Oh ya! I don’t think you’re a "big…deep breaths