That Immune Health bit (above) is something I'd never heard of. Sounds too good to be true- so, queried AI on that and got as follows:

That is a fascinating finding from a study by King's College London and the University of Birmingham.
Researchers found that these older cyclists didn't just have better cardio; their thymus—the organ that produces T-cells for the immune system—wasn't shrinking as it normally does with age. Instead of producing fewer T-cells (which typically happens starting in your 20s), their bodies were churning them out at the same rate as young adults.

I'd sure like to believe that- never heard of such a thing and looked into it a little further as to whether the 60 - 90 minutes three times a week would qualify and was heartened to learn as follows:

performance.

• Frequency and Volume: Riding every three days equates to roughly 2.3 sessions per week. This falls just slightly below the "three times a week" often cited for optimal metabolic shifts, but the 60–90 minute duration per session ensures you are meeting or exceeding the 150 minutes of weekly activity recommended by the CDC and NHS for older adults.
• Intensity Over Distance: The lead researchers, Professor Janet Lord and Professor Steve Harridge, noted that even "modest activity" that makes you "a little out of puff" is what preserves the thymus gland's ability to produce new T cells.
• Thymus Preservation: Your proposed routine is sufficient to maintain the thymic output (new T cell production) that typical sedentary aging normally depletes.