Early 2018, I bought 3 ENEL18 Hahnel batteries for the gripped D500 and added the D850 later, with a 3rd party grip. The biggest saver at the time was buying a Wasabi charger from Amazon. I was told by the manager of London Camera Exchange branch selling me the batteries that they found Hahnel were reliable, as they'd had very low failures with the brand. At the time, this was a substantial saving: Wasabi charger £44.10, Hahnel EN-EL18 £118.79 (and Mcoplus Grip £85.99 with Ex-Pro Nikon BL-5 £10.95). We've had previous peaks in sharing of 3rd party solutions to save costs to afford the Nikon innovation of the year!
As I can remember, the Hahnel's gave many months of reliable service until early 2019. Then these batteries failed to charge fully, even though the charger confirmed Full. Calibration failed. Far worse, I had the odd power crashes in both DSLRs , this being a blank LCD that would then recover.
When I upgraded to a D5, 2+ years ago, I finally owned the genuine Nikon MH26 charger. This also failed with these same Hahnel's, to full charge or calibrate. No idea if this was their cryptic age or glitches after firmware updates of my cameras. Yet the in-camera battery check ranked all the Hahnel as New! (?).
My primary lesson stands in the 2 genuine Nikon ENEL18's, I also bought in mid 2018: when the first batch of the updated 18c's shipped, but there wwas still old stock. So after I grabbed discounted 18'b I also added one of the new model. Both these batteries still work fine today in the D850, D6 and when they were needed, early 2022, in the Z9.
Looking back, the 3rd party batteries did me okay, considering the price; I guess expect the mileage considerate on their price. Be wary of unexpected errors. My main concern is impacts of future firmware updates. Considering where I photograph in central Africa, and the high costs invested, I minimize all obvious sources of gear failure.
I now only buy genuine Nikon batteries. I'm also confident they all charge reliably - calibrate etc - on the new USBC PD MH33, which is one of Nikon's better ideas. This is a big leap forward for travelling and off grid etc. Compared to DSLRs (assuming comparable mileage/day/week) MILCs run down quicker = frequent recharging. Yet another factor is the GPS is always on in my D6 and Z9. Arguably, I expect batteries to have shorter half lives, even though the ENEL18d is 3300 mAh compared to the 2500 mAh of the ENEL18c.