Heart rate range has been a constantly changing thing since I started tracking it in my mid-50s. I don't know why anyone would think that max effort HR or LTHR would stay the same while one aged and while one's fitness changed with the seasons. My HRs were constantly changing. I tested at least once a month if I had not done a ride recently which would test at least LTHR. Usually I had.
If you don't, you're really lost in the woods, not knowing how hard you can go. I knew my exact maintainable HRs for most of the local climbs. It's not hard - just go as hard as you think you can and see what happens. Next time, go either harder or easier, depending. Remember what those numbers were, log them. Most climbs of equal time will have the same numbers. Knowing your numbers will really pay off on the big rides, where you'll know exactly where to park your HR. If you're right, you'll hold those HRs to the end and wind up not being able to dismount the bike. Perfect. It's not possible to see the future many hours away as accurately just gong by feel - or going by power or speed for that matter.
Those numbers always changed as my fitness changed with the seasons and slowly went down at a fairly even and increasing rate as I got older.
If one is using an HRM and doesn't know those numbers, that means that one can go harder, simple as that. If you don't seek your limits, you won't know where they are. OTOH, not everyone is driven to seek them. Maybe it's not even a good idea.
__________________
Results matter