I’m interested to see what my TSS for the gravel event I’ll be doing on Sunday is going to be?
I expect between 350 and 400, depending on youre training history
I dont know, i can do 4hrs on the road pretty easily. 2.5hrs on the trainer and my brain starts to hurt.
You see I’m the complete opposite to this, I would rather do a 2-4 hour ride on the trainer over going outside. 1. It’s way faster (when you factor in preparation to leave the house and if you have to drive to the start of the group ride and back). 2. You can start and stop as you like and just wear bib shorts. 3. If you’re into music and watching a show as a distraction, then you have that to pass the time. 4. It’s more disciplined and structured.
Science and training aspects aside, it’s important sometimes to have some downtime on the bike and enjoy ourselves, our ride buddies’ companionship and the simplicity of a wonderful machine. The love of bicycles is how we got here in the first place no?
I am a single dad and when my kids visit their mother I take time out for ME. Audax (Randonneuring) is my interest, so in answer to the OP’s question: ‘Are long rides necessary?
HELL YEAH! 
^This. 100%
It’s like anything in life - it depends. @brendanhousler is training for a one day 340mi gravel race and did 250 miles solo @ 260w 
4 Tips for Long Distance Cycling | 250 Mile Bike Rides | EVOQ.BIKE
Many a good long ride was started well before the wife and kids awoke. All are planned in advanced and done as efficiently as possible. I don’t see any other way with a 6 yr, 4 yr and 8 mo old. I’ll do my big rides when I’m retired.