I am very sorry you are going through this and having to make these choices. They are hard ones to make, that's for sure. Glad to hear though that it sounds like your treatment thus far has gone to plan and it hasn't spread.

I originally started on Tamoxifen and then was switched to Exemestane when I was also started on Lupron. I didn't noticed too much extreme in the way of side effects from the Tamoxifen, not sure if it was only because I only took it a month or so but I do have many side effects from Exemestane, as well as Lupron and Abemaciclib (which is a different variant of CDK4/6 inhibitor). The Abemaciclib was initially just some upset stomach but over time I added more side effects because it takes time to fully get into and change your system. I have constant high and low flags on my bloodwork from that one. Low HCT, RBC, low WBC and ANC. Very high MCV and MCH. So I can see how it has changed my blood and those changes, especially the low RBC and WBC impacts how I feel. Fatigued, short of breath, dizzy, bruise easy, slow to heal, I have to always be careful of risk of infection and sickness. Sometimes that will be worse than other times, they will tell me it's very low and to not go into crowded places until it is back up to "normal" low.
I also have trouble with my hair, skin and nails. I have had my hair thin to about half of what it was and it looks awful, just dead, straggly, dull with no shine or life at all to it. It also hardly grows, I am always unsure what to do about cutting it because it doesn't really grow back, so it's just getting shorter and shorter. My nails are dry, brittle, cracking, growing split and with deep ridges and almost like white scratches on them and indented areas, and my toenails are almost like concaved in some spots. My skin is so dry, flaky, itchy, just very unhealthy and I feel like it's constantly wanting to peel a layer off when I wash. Almost like it's turn over time is too fast and then the hair is extra slow. I have also always gotten very nauseas if I don't eat when I take both the Abemaciclib and the Exemestane, it was generally ok though if I ate. Now more recently I get nauseas regardless, especially with the Abemaciclib and have started with more upset stomach periodically no matter what I do or eat or don't do or eat. I have been on all these for about2 and a half years now. I also get all the menopause symptoms like constant hot flashes, night sweats, achy joints, heart palpitations, bladder issues (peeing constantly and some leakage), mood swings, very bad brain fog. One of the worst things is that I am constantly tired, just 100% fatigue all the time. I don't know if this is from just one or the conglomeration of treatments.

Everyone is different, so someone who has one side effect may not have another. It's hard having so many different side effects and having to be on so many different meds and I am on them all permanently, until they stop working. Something I can't speak to is how it goes when you go off any of them, like how well you recover from the effects. Hopefully there might be some who can speak to that, because it might be worth trying the added treatment and see how you feel on them. Then just go off them if they make you feel too badly. I personally would not think all my current side effects from them were worth it to be taking all this for only possibly preventing recurrence but everyone and every situation is different. I would rather feel as good as possible for as long as possible, rather than just living as long as possible and feeling terrible the whole time. I actually even feel that way now, knowing it's basically keeping me alive and I debate all the time just stopping them anyway because of my QOL declining so much since treatment began.

I want to be honest about how I feel but I don't want to discourage you from trying them though, because everyone reacts differently to them and I have no doubt they are working to do what they are supposed to do. I had a decent size tumor shrink away into no sign of it in my breast and the cancer has not spread any further. Unfortunately it's still all in my bones, which the treatment doesn't seem to work as well at compared to the soft tissue areas. I even had a spot on my face that I suspected was skin cancer, that used to bleed on and off and it too just went away from the Abemaciclib I assume. So it's pretty amazing stuff.