Classtime 

Before I started doing long rides, I thought it would be boring. I don't get bored. It's weird. When I was doing brevets or preparing for my spring classics, a frequent long ride was 4 loops with a bunch of climbing. Same loop 4 times. As I approached the beginning of the next loop, sometimes I'd ask myself, "Do you really want to?" And then It is always such a kick to keep on riding. I can't imagine riding only for fitness. That would be like mowing the lawn before it needs it. How do you know where you're going?

Jim from Boston

+10 to @JohnJ80 . I too employ tracking, especially mileage, and I do cogitate on things like work issues, and even compose Bike Forum posts in my head. Not to start a popcorn discussion but I also listen to talk shows (link).

I won’t comment about the physiologic issues, but if boredom is a problem, I have also posted about my other mental remedies:

john m flores 

You will get more fit with longer rides with rest days in between. And more importantly, you’ll get out of the rut that it sounds like you’re in. Have fun!

TricycleTom

Thanks for the various points of view. To reduce confusion, the boredom does not hit on the ride itself, but afterwards, when I with I had more time for things of lasting value. I have never been on a group ride. Once or twice a year I meet another cyclist and change my route to chat. I have no apps, just a speedometer. My heart rate monitor thinks I'm dead, and most of my other electronics have problems I can't resolve. There are no significant hills here, just seasonal scenes, wildlife, and weather. I sometimes need granny gears going into the wind, and love spinning hard downwind.
This year, I'll stay home on more marginal weather days, and try to make a treat out of making up the miles with some fresh scenes. I've been poking around the gravel a bit, but rather than ride the slow bike, I'd rather wait for the days when the grid roads are a clay track. Accessing them also means putting up with more crosswind riding.

Boatdriver

You mentioned that you are out for fitness, not competition. Even so, the suggestions above that talk about pushing and recovering are spot on. In "Fast After 50" by Joe Friel, he not only addresses competition, but functional fitness to be able to continue doing what we want as we age. He cites many studies that show a hard workout followed by some recovery is more effective in slowing down the aging process than simple steady state exercise.

TricycleTom

My main health challenge is getting enough sleep. I'll see how days off affect that. The effort does vary considerably with other conditions. This week I easily caught up to another rider, and it turned out to be a younger guy who is locally famous for riding 40 mile loops. I don't know if we could ride together. I paired up with another rider on a tour to help with drafting, and he was used to a gentle warm up. I was used to sprinting to work in the morning. I had to ride my brakes for the first two miles, and then we matched for the rest of the day.

KraneXL

What did you learn from that experience?

TricycleTom

If I'd had anything else to do, I'd have given him a head start, but I guess I learned that sometimes it is OK to waste energy if it saves effort overall. I probably learned a bit about the range of normal physiology, too, which is why I mentioned it.
We had another funny experience after riding together for some weeks. We arrived at a campground on a hill, but wanted to shop in the town in the valley just down the road. We checked our panniers with the Ranger, and headed downhill. Right away, we were both checking our tires for flats, because the bikes were just not accelerating in their usual manner!

bluezurich

I ride about 30 miles a day and make certain I take 1-2 days off during the week. So I agree that a bit more time and milage is better with days off in between.

I make sure my connective tissue gets a break, my enthusiasm stays high and my butt gets some relief as well. I could ride everyday but I would jeopardize one or more of those and potentially screw my riding for the season either physically if mentally (or both)

Take breaks!

wphamilton

For straight up cardio health, half an hour or more of moderate effort every day gets you most of the gains. Rest days are not necessary, skipping days will be less effective.

Improving fitness is a whole 'nother story. At some level of fitness, gains in cardio health will be marginal.

KraneXL

Think of our bodies like an engine. If we run it all the time when will we ever be able to do any maintenance? At some point we have to shut it down for repairs and upkeep. Our bodies repair and grow when its at rest.

Besides, as with anything (event those things that are good for us), there is always a point of diminishing return. Excessive exercise (exercising too hard or too long) will do more harm, than good. Always keep that in mind.

TricycleTom

I'm pretty sure that even 20 hours off the bike gives the bod plenty of time to sneak in some renovations. I recall the story of the first two guys to row from England to NYC. A reporter asked what training they had undertaken. Astonished, one replied "The first week's the training, mate!"
I am fairly sure that days off are bad for my sleep, but they do help persuade me to do my stretches or other PE stuff. Psychologically, it works far better to build up a credit of miles to "spend" on a day off, than to take a day off and then "have" to catch up to the monthly goal. I think it also encourages me to recall the rides I had on the same bike forty years ago.

DaveSSS 

You'll never gain the endurance for long rides if all you do is daily short rides. I used to ride a 50 mile route with over 10 miles of climbing, every other day, from age 50 to 57. I took 8 years off because my knees were shot. I got two new knees in 2017 and started riding again last July at age 65. I advanced from 16 mile rides to 40 mile rides, with lots of steep hills. The hills required lower gears, but we're still tough, compared to a flatter, more boring route. If I do the tough 40, I take two days off to recover. Without the recovery time, you'll get slower, not faster.