On your endurance rides, when (what % FTP) does the ride get too easy? Can an endurance ride be too easy? What’s the training effect difference between 3 hours at 40/50/60/70% FTP?

Have had a few problems with my left leg recently, so contemplating getting dual leg power measurement.

Currently running 12speed Ultegra di2 and I love my TIME XPresso pedals.

Is a 4iii crankset my best bet?

I am wondering how outdoor intervals are done in this community . I do most of my intervals outside but sometimes struggle with terrain. I am getting better at holding power on a downhill but it can get tricky sometimes.
So my question. Say I have an 8min recovery but the next section of terrain is 16min away , can I maintain most of the benefit by increasing power during that rest interval (say upper zone 2 rather than zone 1) or it doesn’t work that way?
I do hill repeats sometimes but that can be quite tedious and limiting and even then my 20min climb would still prob take 10mins to descend . Perhaps overthinking it but would like to maximise quality and enjoyment .

I got a new pair of GP5000 STRs in 35mm. I cracked my old rims so using a cheap and heavy alloy replacement for now. But in searching for a new carbon wheelset want to optimize ideal internal/external width around the 35mm tire.

Should I stick to 21mm internal or would 25mm internal suit this specific tire better?

Last year was my first year of serious training and I was able to progress to high volume quickly with NO problem but after taking a break for 2 months by the end of 2025(less volume and structure but big rides every weekend), I noticed improved durability and speed both when climbing and cruising on flats.

The problem is that my leg would be heavy, for example, with 4h of base ride (something I used to do back to back last year).

Is it simply that I have less power before that I was able to ride so much and doing the same volume today going to require more dialed nutrition and lifestyle?

21 m college , currently 2nd year structured training, 3 years Powerlifting background