I am so happy for your repair. I too have an H2D, for 4 months, and my heater assembly for my Right nozzle failed. After only 4 months and 300 hours, Bambu Labs say that this is an acceptable consumable. How can it go bad after 4 months and low usage? I am very disappointed.
When you choose to underrate or skip maintenance, that’s a good starting point.
If you do maintenance only when prompted by the device, you’re on a good path to be an active part of these topics 
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Really dude, I am doing the maintenance as recommended by the printer and even more. Just asking how do you actually see if these leadscrew are aging faster than they should or how do you see it ? It is not more difficult to answer with a useful answer.
They had some wear but printing was still OK. To detect you just push below the bed to sense the amount of play, you can use a gauge on your toolhead to get the value. After some more wear you will start to hear some slight knocking at every Z-hop. Some have a lot more wear and still printing until the wear is high enough that the thread of the nut strip completely and this is when you know it’s gone 
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Thank you for taking the time to answer. I learned something 
and I will check that from time to time.
Yea no, I have several H2D and a C and I maintenance every print. Like fully degrease and regrease all lead screws. I have had several nut failures in the past and even with my insane maintenance I have blackened grease on my leadscrews after every 24-48 hour print. That black is the brass contaminating the grease. Worn brass in grease = failing leadscrew nuts. Bambu just dropped the ball with these. Low quality nuts and a lack of load balancing. These beds are too big for one bras nut in the rear.
Is your grease turning black? That’s the brass from the nut being ground away. Congratulations! Your nut is failing 
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Damn, then I have it. So you open a case at support to have them replaced ? Mine are 7 months old.
Bambu won’t replace it unless it’s really worn but you can order the leadscrew kit in advance here:
Select your printer in the menu and select the Z-axis leadscrew kit and submit a purchase order
Kind of a waste of money buying parts that fail so quickly.
I have 300 hrs on POM nuts, Still tight. (No black grease)
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Grease becomes black because it oxidize due to metal surfaces contact, it’s normal. 
Then the residual gives the new grease a grey tone,it takes a while to become fully black, I don’t use dental floss to clean screws so a bit of black grease it’s permanently there to mix up with the new one
It is the WD-40 on the rails that evaporates too quick, I am starting to think it’s better to use oil, for a longer lasting lubrication
Printer has 3400h and the only issue is some intermittent squeaking by the free wheels on the back, bed has no free play at all.
So what is the trick to reaching 3400h without failed nuts?
I just talked to support and they said you have to relube the lead screw which means remove every last drop of old grease and putting on new grease once a week or every other week to keep the nuts good edit” ow they also said if you see any bronze dust also do it then”
I was wondering about that, too. You can buy Delrin and slippery Delrin (impregnated with PTFE) rods (I keep a good bit of it on hand). You could turn it to the right diameter and follow that with an ACME thread tap. Stuff machines super easy.
If Delrin outlasts brass significantly, it might be a one-time fix.
If you do not have the tools or a friend that does, Xometry might be a source for custom made parts:
My thoughts on 3D printing threaded parts is that the resolution is not really going to be good and then there are issues with layer adhesion to consider.
Years ago I saw on a machining forum (I forget which one) where someone made the nuts not by machining but by heating the leadscrew and squeezing the Delrin around it to form the threads.
FWIW, we talked elsewhere about POM (acetal, delrin (commercial name) is POM).
Thread is not ACME but metric ISO TR8
Thanks. Taps are available for TR8 threads, but do you know what the thread pitch is?
Not sure I would want to print with POM due to its outgassing.
(EDIT) Pitch is 2mm, TR8x8 rods and nuts.
Bambu’s 6mm tall nut has 3/4 of one full turn of thread.
Aftermarket 16mm tall nuts have 2 full turns of thread.
Actually pitch is 2mm with 4 starts but you’re right one full turn is 8mm displacement
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No way to subscribe to a thread except to make a post and it’s gotta be >25 characters.