As you already heard, there is no linear relationship between platelet levels and thrombosis risk. It is more complex than that. There is an increased risk of hemorrhage as platelet levels get higher however. Platelets at 690 is not particularly high. Some MPN experts use 600 as the target for cytoreduction when a number is used. In the absence of symptoms, particularly thrombosis, it is reasonable to question whether cytoreduction is indicated. Note that any co-occurring conditions, symptoms, or risk factors would alter that decision.

You note that the platelet levels are steadily increasing. It would be reasonable to investigate whether progression of the ET is occurring, though that should not be assumed. This also raises a question about your treatment goals. Are you content to target only short-term management of risks and symptoms or do you wish to make reducing risk of progression a treatment goal?

Suggest that you consult with a MPN Specialist rather than a regular hematologist for the best case-specific advice. This should include all of the options for treating the ET, including the other NCCN first-line cytoreduction option, PEGylated interferon. There may also be drugs in clinical trials that you could consider. There is some evidence that the interferons may reduce the risk of progression. If this is a consideration for you then that would be something to discuss with a MPN Specialist.

Wishing you success moving forward.

Best of mornings Mark, you are getting many suggestions both pro and con
I personally share your thought. "Platelets are not concerning" says my Hemotologist. If they were elevated near 1mil then we would consider treatment.
Remember, our doctors' fundamental protocol is to minimize risk. Being debilitated on the couch, but alive, fits their objective.
I'm in the same situation, but more critical. I have controlled PV but with trending whites I am left with few options. I feel great but high whites it's another elevated thrombosis risk. I declined HU for the same reason. I will begin Besremi in the coming days but not without hesitation. Today I'm thinking, I feel fine, I'm very active, healthy and feel great. I'm not going to take it! But, progression is something which I need to consider. Many risks either way...sucks.
Only you know your physical health, personally I would defer.
Cheers, in moderation.

I started on Hydroxea in August 2019 with severe diarrhea. I started wearing depends and didn’t have a social life. I emailed my oncologist who put me on Pegasys, and was shocked when my body accepted it with no side affects. I’m cruising now with 280,000. I feel good except for the extreme sweating. My daughter calls me m anomaly as I’m so sensitive to medication. I feel blessed I’m cruising!!

Like many PV sufferers, I had hoped to avoid doing anything more than venesections. But my reds did not agree, and overproduction stresses the marrow. The dreaded Hu was offered and declined but in due course it was this or another drug. Ingesting poison??? However my 75 yo body adapted to 500mg, not enough for the rbc control, then 1g. My bloods have been very good for over a year now, side effects only fatigue which we all seem to aget anyhow - and an afternoon nap fixes that. Hu suits me - and my lifestyle of exercise and travel, and living life while I can.
There are some drugs we might hate to ingest, or inject, but sometimes they might help, a lot.

It seems to me that if your MPN/Hematologist recommends pharmaceutical therapy but you are worried about side effects, you can always stop the medication if the s/e are too much. What if you are one of the 50% or 30% or 75% who get relief without side effects? What would that do for your quality of life? Wow! Especially if you have a mutation, all the pure foods and herbs and organics won't change the mutation. There are multiple kinase inhibitors, along with interferons, and possibly other medications that can give relief and possibly change the course of the condition and maybe extend your life expectancy. There are many people on this MPN site who are living with MPN for 10, and 20 years. Many taking medications. This is a chronic condition so with therapy your can extend your years.
My wife is the Jak2 PV patient diagnosed 10 years ago, so you can say to me that it is easy for me to be optimistic since I don't have the condition. Well, I've lived through her pancreatic cancer surgery, removal of her pancreas, spleen, part of stomach, duodenum, and gallbladder. Then her PV diagnosis. Then multiple emergency gastric bleeds due to the stomach acid effect on her anastomoses in her stomach/intestines. And all along helping her with her very volatile type 1 diabetes since the pancreas was removed. So I have lived every bit her pain, scanxieties, digestive problems, and chronic MPN with her. Before taking Jakafi she had itching, daily headaches, dizziness, high blood pressure (even while taking medication for HTN), burning and painful hands and feet along with high platelets. She needed to put her feet into an ice bath every night before bed, in order to sleep. Her PV symptoms ended in 7 to 10 days when taking Jakafi. Still some itching at times, but no more daily headaches, no dizziness, her BP is normal, very rarely does she have foot and hand pain. And her Hemoglobin/Hct and platelets are within reference range. Her QOL has returned.
I wish you all control of your conditions and happy long lives.