If all the pack has ridden off and left you, then maybe you need to find another pack or get some that ride at your level involved and riding with your pack.

However, I'm a little puzzled or surprised by the low numbers you claim for HR max and recovery times. Have you talked to a real heart doctor? I know that at our age we are supposed to have lower HR max and other things, but I've never known anyone that regularly gets cardio, even when taking off a year or so have the numbers you mention. But I"m not quite your age so maybe that's to happen yet.

If a full cardio workout is within your health abilities, I'd think limiting your HR and never going above a bad thing. For certain you may not need or want to spend a lot of time at the anaerobic levels I or others might do, because it's not necessarily making us better performing, it just fills an addiction. However you should be able to put out a good effort on climbs and sometimes flats for a sprint then see you HR come back to some level that you allows you to finish with comfortable energy reserves what ever distance you are cycling that day.

Shorter trips, I usually have a higher average HR. Longer trips usually have a lower average HR. But I still end longer trips with the same speeds as shorter ones. Just that I can't maintain those speeds for as long a time.

Also, do you replenish most of the carbs you burn on rides? If not, there's a problem to think about if these rides you are talking about are a couple hours or more in time.