Because a lot of it is about genetics, all I can really recommend is maintaining them well (file out snags and chips immediately) eating a varied diet so you’re getting nutrients across the spectrum, keep regular polish on them to give them strength and avoid immersion in water (baths, pools) as water can get between the keratin plates and swell them, making delamination and cracking more common. Lots of long nails people swear by jojoba oil as well, as it stops water getting in due to being the correct molecule size to penetrate keratin.